Re: [AMRadio] Using Heath SB 610 Monitor Scope tomonitormodulationonAM transmitter
The 620 is a panadapter. It requires a connection to the mixer plate (or input side of an IF chain). The 610 (for receive) requires a connection to the output side of the IF chain. Pete, wa2cwa http://www.manualman.com On Mon, 11 Feb 2008 21:49:28 -0600 Jim Wilhite [EMAIL PROTECTED] writes: Bingo you are right Bob. I just traded my 620 and did have them backwards. The 620 requires a connection to the IF of the receiver. Jim/W5JO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] Using Heath SB 610 Monitor Scope to monitor modulation
I use a highly modified HO-10, which is basically the same scope in a different package. I used to use the trapezoid pattern all the time. Mine is wired up with the t/r relay system to deflect the spot off the tube when the transmitter is in standby mode. But I found that with the trapezoid that the unmodulated carrier eventually burnt a vertical line on the scope tube, even though it registered only briefly between syllables. I now use the envelope pattern to monitor modulation, and use the trapezoid only to check modulation linearity. In evelope pattern, the horizontal base line appears only on cw, during key-up conditions. I work some cw, but not enough to burn a line on the scope. I like to monitor my cw waveform just like I monitor my modulated waveform on phone. Don k4kyv __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] Todays Toy - Elmac PS-2V
Wow, very clean. Where did you score this purchase? Mike WE0H JT Croteau wrote: FedEx just delivered me an Elmac PS-2V power supply that I plan to use with an AF-68 transmitter that should be arriving any day now. It is very clean and includes the CFS-1 cable and PTR-1 relay kit. It has had one mod done to it however. Someone has added another 6.3V filament transformer under the hood and a 3-prong male connector to the CFS-1 cable, Have not investigated the reason for both of these yet. Pics: http://n1ese.qrpradio.com/Elmac/ __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] Todays Toy - Elmac PS-2V
On Feb 12, 2008 3:35 PM, Greg [EMAIL PROTECTED] wrote: The original relay probably pooped out and was substituted with a six volt DC relay. Well, that would make sense but the relay installed is a 24V relay. Heh. -- JT Croteau, N1ESE - Manchester, NH (FN42gx) Contest Manager, TARA Skirmish __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] Todays Toy - Elmac PS-2V
The original relay probably pooped out and was substituted with a six volt DC relay. The extra connector on the end of the cable is most likely for the mobile receiver or front end converter. I got a bad feeling that the AF 54 67 and 68 will be going up in price soon due to the demand for quality plate modulated stuff. Thanks for the FB pic's JT 73's Greg WA7LYO Kinston NC - Original Message - From: JT Croteau [EMAIL PROTECTED] To: Discussion of AM Radio in the Amateur Service amradio@mailman.qth.net Sent: Tuesday, February 12, 2008 2:58 PM Subject: Re: [AMRadio] Todays Toy - Elmac PS-2V Update on my PS-2V.. The relay kit installed is not the original PTR-1 kit that was put together by Multi-Products. This relay is a Western Electric 24V unit where the original supplied was a 24V Potter Brumfield unit. The relay is supposed to be powered by the 24V tap coming off the filament transformer. However, this installation is powered by the dedicated 6.3V transformer that has been mounted to the top of the plate tranny. There are then three diodes and a big 1000 uF capacitor in between the 6.3V tranny and the relay. I don't understand why it was done like this at all. -- JT Croteau, N1ESE - Manchester, NH (FN42gx) Contest Manager, TARA Skirmish __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] Collins 21-E FS on QTH
K6OR has a Collins 21-E BC transmitter for sale on QTH(ad#646866).Has crystals for 75m ghetto, 5kW high, 1100 watts low.$5K.Usual disclaimers apply. Joe W4AAB __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] HT-32/SX-101/NC-183D
He is in Amarillo, TX. Jim/W5JO WA5NKP has the above for sale on QTH(ad#646751). Usual disclaimers apply. Joe W4AAB __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] RE: Using a Ranger as a driver
Gary, That is exactly what I meant by the sweet spot in the final current. By dropping the screen voltage only, it would allow better modulation and also reduce saturation. I found that my VKII had the best audio and mod % when run at about 90 watts on the TenTec tuner meter. Reference only really.Plate current was reading no more than 190-200ma and mod current swinging to about the same on peaks. Not sure just how accurate the stock meter is. The meters had different dynamics in the 2 VKs that I used to run. Been about 5 years ago and the 807s were driven by a UTC line to grid directly from the audio rack. This has been a great thread ! Thanks, Bill, KB3DKS in 1 land -Original Message- From: Gary Schafer Subject: RE: [AMRadio] RE: Using a Ranger as a driver SNIP When reducing power by reducing screen voltage the plate voltage is going to remain the same and plate current is going to be less, so the plate impedance will be higher and the modulator will see a higher impedance also. Now the modulator will not be able to produce as much power as it did before because the modulator plates will flat top (go into limiting) with the lighter load on them. That is if you try to pull the same amount of audio out of them as you did before when they were working into the lower load impedance. But this is not a bad thing because with reduced power in the final you don't need as much audio to modulate it with. The load impedance that the modulator tubes see is not important as long as it is low enough to be able to produce enough power to fully modulate the transmitter before the modulator tubes voltage swings to the saturation point. If the load impedance is too low the tubes will work too hard trying to produce enough power out and will operate in the non linear part of the plate curve. Some transmitters are deliberately designed to have the modulator tubes flat top and act as limiters to keep the modulation percentage below 100%. The venerable Johnson Viking 2 is such an example. The modulation transformer that they chose provides a little too high a load impedance to the modulator tubes so that they go into clipping before 100% modulation is achieved. Their idea of a soft clipper. 73 Gary K4FMX More new features than ever. Check out the new AOL Mail ! - http://webmail.aol.com __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] RE: Using a Ranger as a driver
Hi Jim, I think what John is saying is that you do NOT want to retune when you lower the plate voltage in order to maintain the same plate impedance. If you were to half the plate voltage with a modification to the transmitter then during tune up you would want to tune up to half the plate current that you had with full voltage before the modification. That will give you the same plate load impedance and the modulator tubes will see the same impedance. You are now operating at 1/4 the power you were when you had twice the plate voltage. But maintaining the same load impedance on the modulator is not necessarily important: See below. When reducing power by reducing screen voltage the plate voltage is going to remain the same and plate current is going to be less, so the plate impedance will be higher and the modulator will see a higher impedance also. Now the modulator will not be able to produce as much power as it did before because the modulator plates will flat top (go into limiting) with the lighter load on them. That is if you try to pull the same amount of audio out of them as you did before when they were working into the lower load impedance. But this is not a bad thing because with reduced power in the final you don't need as much audio to modulate it with. The load impedance that the modulator tubes see is not important as long as it is low enough to be able to produce enough power to fully modulate the transmitter before the modulator tubes voltage swings to the saturation point. If the load impedance is too low the tubes will work too hard trying to produce enough power out and will operate in the non linear part of the plate curve. Some transmitters are deliberately designed to have the modulator tubes flat top and act as limiters to keep the modulation percentage below 100%. The venerable Johnson Viking 2 is such an example. The modulation transformer that they chose provides a little too high a load impedance to the modulator tubes so that they go into clipping before 100% modulation is achieved. Their idea of a soft clipper. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Jim Wilhite Sent: Tuesday, February 12, 2008 10:00 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] RE: Using a Ranger as a driver Ok John, I have but a few observations and questions that might steer everyone through this. I am having trouble understanding how the Z the modulator see is greater if the plate load impedance goes down. If the Plate Z is = to the Ep divide by 2 times the Ip and you change one value how does the Z remain the same. Even if you maintain the same ratio doesn't the plate Z change as a result? In your example you change both at the same ration which maintains the same impedance. Ep 600 Ip200 ma. Zp= 600 divided by 2 times .2 = 600/.4 = 1500 Ep300 Ip100 ma. Zp = 300 divided by 2 times .1 = 300/.2 = 1500 The ratios stay the same, but what I question is if you reduce the plate voltage of a tube but load it to the same value of Ip or near it, the impedance changes on the secondary of the mod transformer, which I guess, is where the divide is. I have seen many people make this mistake. Because if you do, to maximize power or whatever reason, the impedance seen by the primary of the mod transformer is not optimum. In the discussion of the way to drive the amplifier no one pointed out that you must maintain the ratio of Ep to Ip. This is where I kept sticking. Now the question becomes, why did Johnson say to load the Ranger to rated plate voltage and current but insert the pad between the transmitter and amplifier? Just guessing here, but I would bet that amateurs of the 50s were much like those of today. All knobs and stated reading must be to the right. Or is there something that is seen on the primary of the mod transformer by the Class A or B modulator tubes we haven't discussed yet? Jim/W5JO Hi Jim, What I said was, or tried to say, when a Class C rig is unloaded so as to draw less current, that is, to tune the loading and plate circuit so that the plate dip is lower current than it was when it is tune up for max. The plate voltage will stay about the same but the plate current is less and you have less RF output as well of course. In this scenario the ratio of Ep / Ip is greater. The Z that the modulator sees is greater. Now if the plate voltage is lowered with out retuning anything, the plate current will fall as the plate voltage falls and the ratio of the two remains the same. Basically when a class C rig is set and not retuned, the Ep:Ip ratio is set and the plate current should follow the plate voltage up and down linearly. The RF should follow the plate voltage up and down as well. Some tubes and circuits need a little help with this. Such as using grid
Re: [AMRadio] 1N91 Substitution
NTE 116 is the generic cross. Jim/W5JO http://www.nteinc.com/ What can I substitute today for a 1N91 rectifier? Thanks -- JT Croteau, N1ESE - Manchester, NH (FN42gx) __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] RE: Using a Ranger as a driver
Ok John, I have but a few observations and questions that might steer everyone through this. I am having trouble understanding how the Z the modulator see is greater if the plate load impedance goes down. If the Plate Z is = to the Ep divide by 2 times the Ip and you change one value how does the Z remain the same. Even if you maintain the same ratio doesn't the plate Z change as a result? In your example you change both at the same ration which maintains the same impedance. Ep 600 Ip200 ma. Zp= 600 divided by 2 times .2 = 600/.4 = 1500 Ep300 Ip100 ma. Zp = 300 divided by 2 times .1 = 300/.2 = 1500 The ratios stay the same, but what I question is if you reduce the plate voltage of a tube but load it to the same value of Ip or near it, the impedance changes on the secondary of the mod transformer, which I guess, is where the divide is. I have seen many people make this mistake. Because if you do, to maximize power or whatever reason, the impedance seen by the primary of the mod transformer is not optimum. In the discussion of the way to drive the amplifier no one pointed out that you must maintain the ratio of Ep to Ip. This is where I kept sticking. Now the question becomes, why did Johnson say to load the Ranger to rated plate voltage and current but insert the pad between the transmitter and amplifier? Just guessing here, but I would bet that amateurs of the 50s were much like those of today. All knobs and stated reading must be to the right. Or is there something that is seen on the primary of the mod transformer by the Class A or B modulator tubes we haven't discussed yet? Jim/W5JO Hi Jim, What I said was, or tried to say, when a Class C rig is unloaded so as to draw less current, that is, to tune the loading and plate circuit so that the plate dip is lower current than it was when it is tune up for max. The plate voltage will stay about the same but the plate current is less and you have less RF output as well of course. In this scenario the ratio of Ep / Ip is greater. The Z that the modulator sees is greater. Now if the plate voltage is lowered with out retuning anything, the plate current will fall as the plate voltage falls and the ratio of the two remains the same. Basically when a class C rig is set and not retuned, the Ep:Ip ratio is set and the plate current should follow the plate voltage up and down linearly. The RF should follow the plate voltage up and down as well. Some tubes and circuits need a little help with this. Such as using grid leak resistance instead of a fixed supply if the stage is to be modulated. The grid leak resistance will allow the grid voltage to fluctuate a little with the audio as the plate current goes up and down. This actually helps to keep the ration of IP to EP constant. The grid leak resistor is something of a self regulator for the ratio. The screen grid tubes have a whole other set of things that can be done to help the plate current to plate voltage ratio remain constant. There was a discussion awhile back about the plate voltage to plate current ratios. Some one was saying that a circuit will lose efficiency if the plate voltage is reduced. This is only true if the person changes the loading or tuning. What they probably meant was that if you reduce the voltage and try to retune to get the same power out that you would have less efficiency. The only thing that should happen when plate voltage is reduced is that the power input goes down and the RF power also goes down. If a rig with a plate supply of 600V is putting out 100 watts into 50 ohms the RF voltage would be 70.7 volts RMA. When the plate voltage is reduced to 300V the rig should put out 25 watts with RF voltage of 35.35 RMS on the load. Here is a chart. 600V EP 200ma IP DC input power = 120 watts RF output 100 watts Plate dissipation = 20 watts EFF = 83 percent EP/IP = 3000 ohms modulator load Z Now let's go down to 300 volts on the plate 300V EP 100ma IP DC input power = 30 watts RF output 25 watts Plate dissipation = 5 watts EFF = 83 percent EP/IP = 3000 ohms modulator load Z __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] 1N91 Substitution
What can I substitute today for a 1N91 rectifier? Thanks -- JT Croteau, N1ESE - Manchester, NH (FN42gx) Contest Manager, TARA Skirmish __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] HT-32/SX-101/NC-183D
WA5NKP has the above for sale on QTH(ad#646751). Usual disclaimers apply. Joe W4AAB __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] Todays Toy - Elmac PS-2V
I just bought an AF-67. I have two A-54H(not AF)transmitters I need to get sold or traded once I get them working.Nothing like plate modulation. Joe W4AAB - Original Message - From: Greg [EMAIL PROTECTED] To: Discussion of AM Radio in the Amateur Service amradio@mailman.qth.net Sent: Tuesday, February 12, 2008 2:35 PM Subject: Re: [AMRadio] Todays Toy - Elmac PS-2V The original relay probably pooped out and was substituted with a six volt DC relay. The extra connector on the end of the cable is most likely for the mobile receiver or front end converter. I got a bad feeling that the AF 54 67 and 68 will be going up in price soon due to the demand for quality plate modulated stuff. Thanks for the FB pic's JT 73's Greg WA7LYO Kinston NC - Original Message - From: JT Croteau [EMAIL PROTECTED] To: Discussion of AM Radio in the Amateur Service amradio@mailman.qth.net Sent: Tuesday, February 12, 2008 2:58 PM Subject: Re: [AMRadio] Todays Toy - Elmac PS-2V Update on my PS-2V.. The relay kit installed is not the original PTR-1 kit that was put together by Multi-Products. This relay is a Western Electric 24V unit where the original supplied was a 24V Potter Brumfield unit. The relay is supposed to be powered by the 24V tap coming off the filament transformer. However, this installation is powered by the dedicated 6.3V transformer that has been mounted to the top of the plate tranny. There are then three diodes and a big 1000 uF capacitor in between the 6.3V tranny and the relay. I don't understand why it was done like this at all. -- JT Croteau, N1ESE - Manchester, NH (FN42gx) Contest Manager, TARA Skirmish __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] Todays Toy - Elmac PS-2V
On Feb 12, 2008 4:28 PM, [EMAIL PROTECTED] wrote: 24VDC relay installed vs. 24VAC original (just guessing)? 24VDC in both - Original schematic shows a 24VDC relay connected to the 24V tap on the tranny with a 1N91 rectifier and filter cap. This replacement relay says 24V as well but wired to a dedicated 6.3V tranny with 3 diode rectifiers and two filter caps. Not sure what the values are on the diodes as I haven't dissected yet. -- JT Croteau, N1ESE - Manchester, NH (FN42gx) Contest Manager, TARA Skirmish __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] RE: Using a Ranger as a driver
Hi Jim, What I said was, or tried to say, when a Class C rig is unloaded so as to draw less current, that is, to tune the loading and plate circuit so that the plate dip is lower current than it was when it is tune up for max. The plate voltage will stay about the same but the plate current is less and you have less RF output as well of course. In this scenario the ratio of Ep / Ip is greater. The Z that the modulator sees is greater. Now if the plate voltage is lowered with out retuning anything, the plate current will fall as the plate voltage falls and the ratio of the two remains the same. Basically when a class C rig is set and not retuned, the Ep:Ip ratio is set and the plate current should follow the plate voltage up and down linearly. The RF should follow the plate voltage up and down as well. Some tubes and circuits need a little help with this. Such as using grid leak resistance instead of a fixed supply if the stage is to be modulated. The grid leak resistance will allow the grid voltage to fluctuate a little with the audio as the plate current goes up and down. This actually helps to keep the ration of IP to EP constant. The grid leak resistor is something of a self regulator for the ratio. The screen grid tubes have a whole other set of things that can be done to help the plate current to plate voltage ratio remain constant. There was a discussion awhile back about the plate voltage to plate current ratios. Some one was saying that a circuit will lose efficiency if the plate voltage is reduced. This is only true if the person changes the loading or tuning. What they probably meant was that if you reduce the voltage and try to retune to get the same power out that you would have less efficiency. The only thing that should happen when plate voltage is reduced is that the power input goes down and the RF power also goes down. If a rig with a plate supply of 600V is putting out 100 watts into 50 ohms the RF voltage would be 70.7 volts RMA. When the plate voltage is reduced to 300V the rig should put out 25 watts with RF voltage of 35.35 RMS on the load. Here is a chart. 600V EP 200ma IP DC input power = 120 watts RF output 100 watts Plate dissipation = 20 watts EFF = 83 percent EP/IP = 3000 ohms modulator load Z Now let's go down to 300 volts on the plate 300V EP 100ma IP DC input power = 30 watts RF output 25 watts Plate dissipation = 5 watts EFF = 83 percent EP/IP = 3000 ohms modulator load Z -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jim Wilhite Sent: Tuesday, February 12, 2008 11:36 AM To: amradio@mailman.qth.net Subject: [AMRadio] RE: Using a Ranger as a driver I forgot to mention John, you might explain how a Class C final sees higher impedance when the plate voltage is lowered. As I recall Zp is = Ep/(2X) Ip. So a Ranger with 600 V. on the plate with 120 ma. is seeing ~ 2500 ohms. With 300 volts at the same current, it should be seeing ~1250. Zp. Maybe this will help some of these people and you are much more eloquent than I. Jim/W5JO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
AM Mobile Rig (was Re: [AMRadio] Todays Toy - Elmac PS-2V)
- Original Message - Subject: Re: [AMRadio] Todays Toy - Elmac PS-2V Date: Tue, February 12, 2008 16:32 From: Todd, KA1KAQ [EMAIL PROTECTED] I was thinking of your mobile set up Larry, and wondering if it was somehow meant to work with a Gonset converter or ? ~ Todd, KA1KAQ Hi Todd, Not sure I understand the question. My mobile station is an Elmac A54-H XMTR, with the RCVR being a Gonset Super-6 converter feeding the AM broadcash radio. The output of the converter is somewhere near 1400 Kc/s. Antenna is the convenient but innefficient Webster Bandspanner. The A54-H is powered from a PE-103 dynamotor, and the Gonset converter has its own transistorized multivibrator supply strapped on the back to provide plate voltage. If you look at the photo on my homepage (ne1s.rfburn.org), the box below the transmitter takes care of such things as TR switching, RX muting, frequency spotting, switching the AM broadcash radio between antenna and converter, etc. Even have a noise clipper down there, but it wasn't very effective, so I don't use it. Probably more than you wanted to know :-) 73, -Larry/NE1S __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] Todays Toy - Elmac PS-2V
On Feb 12, 2008 4:28 PM, [EMAIL PROTECTED] wrote: - Original Message - 24VDC relay installed vs. 24VAC original (just guessing)? I was thinking of your mobile set up Larry, and wondering if it was somehow meant to work with a Gonset converter or ? ~ Todd, KA1KAQ __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] Todays Toy - Elmac PS-2V
- Original Message - Subject: Re: [AMRadio] Todays Toy - Elmac PS-2V Date: Tue, February 12, 2008 15:43 From: JT Croteau [EMAIL PROTECTED] On Feb 12, 2008 3:35 PM, Greg [EMAIL PROTECTED] wrote: The original relay probably pooped out and was substituted with a six volt DC relay. Well, that would make sense but the relay installed is a 24V relay. Heh. 24VDC relay installed vs. 24VAC original (just guessing)? -Larry/NE1S __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] Todays Toy - Elmac PS-2V
Update on my PS-2V.. The relay kit installed is not the original PTR-1 kit that was put together by Multi-Products. This relay is a Western Electric 24V unit where the original supplied was a 24V Potter Brumfield unit. The relay is supposed to be powered by the 24V tap coming off the filament transformer. However, this installation is powered by the dedicated 6.3V transformer that has been mounted to the top of the plate tranny. There are then three diodes and a big 1000 uF capacitor in between the 6.3V tranny and the relay. I don't understand why it was done like this at all. -- JT Croteau, N1ESE - Manchester, NH (FN42gx) Contest Manager, TARA Skirmish __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] Todays Toy - Elmac PS-2V
On Feb 12, 2008 2:00 PM, Mike WE0H [EMAIL PROTECTED] wrote: Wow, very clean. Where did you score this purchase? qth.com :-) -- JT Croteau, N1ESE - Manchester, NH (FN42gx) Contest Manager, TARA Skirmish __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] RE: Using Heath SB 610 Monitor Scope to monitor modulation
From: W6OM [EMAIL PROTECTED] ... I have two, one connected to the plate of the 2nd IF on an NC 300 for monitoring the incoming signals and for transmit it monitors a Ranger driving an SB 220 on AM. The second on is connected to the grid of the 2nd detector stage on my 75A4 to monitor incoming signals and also watch my transmit signal on a Bauer 707 converted to 75 meters. You are much better off monitoring your transmitted signal using a sample of the signal goind directly to the antenna, than using the output of the detector stage of your receiver. The receiver will inevitably alter the waveform of the signal. There are nonlinearities in the amplifier stages, but most significantly, the i.f. transformers and selectivity filters may completely change the appearance of the envelope pattern. The only way to avoid this would be to use a selectivity that is many times wider than your transmitted signal. Selectivity in the i.f. will cause phase shifts, as well as filter away higher frequency components of the waveform, leaving you a false image of your signal. I don't even like to use the built-in vertical amplifier. The most accurate image is obtained by feeding the deflection plates of the scope tube directly with the rf sample. I use a highly modified HO-10. I believe it is the same scope, with a different style cabinet. It even has the same problem with those 1600V caps. Mine had loads of built-in hum and the image was fuzzy when I first got it going. The Heath manual says not to worry about that; it's inherent to the design, and won't make the scope any less useful for modulation monitoring purposes. What a load of crock! The designers were either incompetent, too lazy or in too much of a hurry get the thing into production, and they probably didn't want to run up the cost any more by using a real magnetic shield for the CRT. I was able to get a sharper image by adding astigmatism control to the scope tube circuitry, and to get rid of the hum (which was modulating not only the horizontal pattern, but the brightness of the pattern, too), I re-routed the filament wiring, using a wire lead for both sides of the filament line, not the chassis base for one side (figured those mods out, one at a time, by trial-and-error). The piece of tin they wrap around the neck of the scope tube is totally worthless as a magnetic shield. I found an old military surplus gadget in my junk pile, that used the same size scope tube (I think it was some kind of RTTY monitor), and used the black anodised metal magnetic shield that was in that unit. That fixed probably 75% of the rest of the hum. I then further reduced the remaining hum by beefing up the power supply filtering. Hard to imagine a more versatile inexpensive monitor scope available now days as they sell for anywhere from $60.00 to $80.00 on eBay and else where. If the face plate is good, cabinet paint is available from a couple of sources and if needed to match a vintage IF strip 455Khz IF cans are cheap and plentiful at Tubes and More in Phoenix for less than $3.00. One word of caution, every one I have owned has had the 1600V mylar caps go bad, so if you buy an SB610 order some replacements ($12.00 from Mouser) and replace them first. With the HO10, and I assume with the SB-610, the power transformer is another troublesome component. The xfmr in my original one crapped out with a dead short somewhere in the winding. I found another HO-10 at a hamfest that had been dropped, for $10. The cabinet was mangled, but all the components were still there and intact, including the scope tube. I used it as a parts rig, and dropped the xfmr into my original one and restored it to operation. Since then, I have found another one for a back-up parts rig. So I have a spare power xfmr, compactron tubes, and a couple of spare scope tubes. Since I don't use mine with SSB, and don't use the vertical amplifier, I pulled the tubes from both of those stages, just keeping the tubes that operate the horizontal sweep circuitry. That liberated some spare compactrons, plus it lightens the load on the power transformer, and hopefully that will make it last longer. So for, after nearly 10 years, that replacement transformer has held up. Don k4kyv __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] RE: Using a Ranger as a driver
Jim: I was under the impression it was *screen* voltage that was lowered. So plate voltage stays put and plate current goes down, yielding a higher load impedance on the modulator. - Jim WB6BLD __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] A productive Morning
Good morning, troops! Today Today, I was able to wake up, walk, talk and complain about things I can -not- change! Today, I am TOO Blessed, to be Stressed! :-) So, while we're on the positive side of things, I think I've managed to incorporate new/old technology out in the ham-shack. Hear me out. The final is home-brewed. I'm sure you already knew that, and it runs a pair of 250TH's in push-pull, class C. Well, what you may not know is that now I have -two- RF finals, that incorporate the 250TH tubes. The original was built by a dear friend of W5BU/Dan(sk) back in the mid 50's. This one I'm using now, was built by Mike/W5IMF in the early/mid 60's. Thanks to my good friend, Duie/K5KZQ, I was able to obtain this good ol' boat-anchor and put it back on the air after 40 years of collecting dust. Works great, too ;-) NORMALLY, I would drive it with the Viking II, like I do the Titanic final, but the grid input is different on the 'new' final. In order to maintain around 125mA of grid drive (250TH's require 45mA per, for Class C. That's 90mA for a pair. Running another 15mA of grid drive on each ain't gonna hurt them big jugs ;-)) Using the Viking II, this wasn't an issue for the plug-in coil and swinging link arrangement on the original final. On the 'new' one, I've got to slip in the 160m coil, re-dip the final, unload it as much as possible and then back off of the grid drive. You know what happens to tubes in Class C when they don't have sufficient grid drive, and full plate voltage... run-a-way current shoots sky-high and there's nothing to stop it. There's protective bias on the 6146 finals of the Viking II, and I'm -sure- that's the only thing that's kept those tubes from shooting up outta their sockets like little glass rockets! What I have done in the past, with this 'new' final, was to use my little Kenwood TS-450S, all band/all mode xcvr as the RF driver. But, it takes around 35~40w to get the grid drive to the 125mA level. Kinda hard to tame a Viking II down to that level, and it's kinda hard on a solid-state rig, with the long ol' buzzard transmissions I tend to make (so I'm told) ;-) Soo... A while back, Rick/K5IAR and I made a deal on a Globe Linear. This thing uses 4 sweep tubes, something like 6DQ6's or some such. So, I got it out, hooked it up, fed RF into the darn thing, and hung it on an antenna. It'll produce around 200w output with 50w of drive from the solid-state exciter. Not bad. Then, I backed off on the carrier and power controls on the little solid-state exciter and got the exciter/amp lash-up down to a more 'reasonable' level for driving the final. Then, I connected it to the final, made some minor tuning adjustments on the grid input and voila(!) the solid-state exciter is making around 4 or 5 watts output, (no danger of hurting anything there) the Globe linear amplifier is making enough output at about 1/4th (or less) of it's maximum output, and that drives the 250TH grids right to 125mA, and it -stays- there. Nothing is wavering. Kewl! All that's left to do now, is find a set of relay contacts that I can use to key the exciter, or use the exciter to key a relay that will, in turn, activate the 110vAC T/R relay. I think the last thing I want to do, is try to make/break 110vAC out of the back of the solid state rig ;-) I think what I -really- need to try to find, is one of the dual SO-239 Dow-Key T/R Relays, and that way I could also use the Solid-state rig as the station receiver, as well. The Globe Linear does -not- have T/R switching in it. Currently, the original T/R relay is doing a good job of switching the antenna between the RCA AR-88 (Thanks to Jim/WD5JKO for the receiver) and the transmitting side of the relay. With it's 'direct frequency entry' keypad, I'd like to be able to use the Kenwood as a receiver, also. Maybe instead of, as opposed to 'in addition to'. (no, the AR-88 is -not- for sale). So, after the story, what I'm asking for is; does anyone have a dual SO-239 Dow-Key T/R relay they would be willing to part with? As always, 'deal' mails should be sent off-list. Discussion about the setup would be encouraged to be conducted -on-list-. Thanks for your time, patience and consideration. -- Driving your AM Rig without a scope, is like driving your car at night, without headlights. (K4KYV) -- 73 = Best Regards, -Geoff/W5OMR __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] Todays Toy - Elmac PS-2V
FedEx just delivered me an Elmac PS-2V power supply that I plan to use with an AF-68 transmitter that should be arriving any day now. It is very clean and includes the CFS-1 cable and PTR-1 relay kit. It has had one mod done to it however. Someone has added another 6.3V filament transformer under the hood and a 3-prong male connector to the CFS-1 cable, Have not investigated the reason for both of these yet. Pics: http://n1ese.qrpradio.com/Elmac/ -- JT Croteau, N1ESE - Manchester, NH (FN42gx) Contest Manager, TARA Skirmish __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] Ranger driving SB220
It is also easy for the modulator to over modulate because it doesn't need to deliver as much current. John, WA5BXO This is probably the main cause of trouble using an amp with a driver as described. I constantly hear crappy audio on the bands with the configuration. Many do not understand meter readings of Class A, AB and B amps anyway so they tend to overdrive them with audio. Not only that they do not monitor the output waveform. Additionally many do not know how to interpert what they see. So all in all, I believe, the best way to avoid hidden troubles is to operate an exciter or transmitter is near its design parameters and reduce power with the attenuator. Last night was a perfect example. One station who was using a solid state exciter to drive a tube amp was splattering all over the place and the person (s) he was in contact with could not hear the problems. If they did, they either wouldn't tell him or did not know what was happening. I was about 5 kc below and when I heard the buckshot tuned up to see who it was. They were all telling him that he sounded fine and what the meters should read. Wrong of course. All this assumes the exciter is operating properly. That can be a crap shoot with a lot of this old gear. Especially a transmitter pulled from a barn and put on the air with mimimual rework. Jim/W5JO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] Using Heath SB 610 Monitor Scopeto monitor modulationonAM transmitter
Ron, I suggest you hook the monitor scope to the grid of the 1st. IF tube. The reasoning behind this is non-linearity is reduced to some extent. I had a hookup to my receiver one time and when people found out they wanted reports on their envelope. Well there are many things that will affect that pattern. The SB 614 I owned had some 60 cycle hum in it and it is very difficult to get out. If you notice in the manual of the 614 Heath said to put an RCA plug with a very short piece of wire attached from the center pin to ground into the Vertical Input jack. The purpose is to eliminate any 60 cycle pickup and introducing additional distortion on the displayed pattern. So after a couple of times of people wanting reports, I disconnected it to keep from trying to explain what I was seeing. Most people wanted quality reports and I wasn't comfortable explaining that what I saw might not be what they were transmitting. To be accurate you need to check the linearity of all the stages preceding the attach point. If you seen much, be hesitant about giving reports. This hook up is kind of all right for baseline reports but the linearity of the received wave will be affected by the distortion you have in your receiver. If the distortion is low, you are good to go, if it is high then you won't be telling the guy the entire picture. Get a distortion analyzer and check your receiver to get an estimate of how much distortion is present before you get to technical. Don/K4KYV found some problems with his HO 10 and had to modify it to correct the problems. He might explain which would help you. Jim/W5JO Thanks Jim You make excellent and insight points as always. I have encountered the issues you speak about in interfacing my 610's with various vintage receivers like my NC-300 and 75A4. Thank goodness that I stumbled across small 455Khz and other frequencies IF cans at Antique Electronics Supply in Phoenix. With some minor surgery both 610's are monitoring received signals on my receivers. On the NC-300 I went directly to the plate of the 2nd IF and coupled it through a 5PF mica. On the 75A4 I went to the grid of the 2nd detector tube and used 4.3 PF mica. Both have full deflection and ad a bit of fun to monitoring by being able to see the everyone's signal. But then, it has been mentioned from time to time that I am a tad obsessive about these beautiful old boat anchors. Cheers my friend Ron Weaver W6OM __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Ranger driving SB220
Hi Jim, Yes, if you change the loading so as to draw less current in the final then the modulation circuit will see higher impedance. In this case, the change to a higher Z load for the modulator is not a bad thing. Audio out put stages will generally produce cleaner audio when they don't need to work so hard at delivering the current. It is easier for them to get the modulation audio voltage necessary for 100 percent modulation when the impedance they see is higher and less current is on demand. OTOH, lowering the voltage to the final (only the final) with out changing the loading will reduce current and voltage so that the load resistance that the modulator sees is the same as before. But less modulation voltage will be required to hit 100 percent of the new DC voltage. The thing to watch on tetrode finals is the screen current. As you reduce the loading on the plate the screen current will rise. This is not to bad (although worth looking in to) if the screen gets its DC and modulation from the plate supply point, but if there is a separate screen supply then you will need to adjust it down to prevent excessive screen current. All in all, the best way to reduce power for a driver /linear combo is to reduce the plate / screen supply voltage for the driver final only, via a dropping resistor or a separate power supply for that tube only. There are other considerations about reducing the load on a final, as the RF voltage at the plate of the tube will increase and may cause arcing of the plate tuning cap or some other component. It is also easy for the modulator to over modulate because it doesn't need to deliver as much current. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jim Wilhite Sent: Tuesday, February 12, 2008 8:16 AM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Ranger driving SB220 I see this discussion every so often and wonder something. If you lower the plate voltage or current the final (s) draw, what is happening to the impedance the modulation transformer sees? The design of a class C final looks at the plate load impedance of the final. If you alter that, the modulation transformer sees another impedance and may not work properly. Some instruction manuals point this out in them. The manual for my Globe Champ says to load to 320 ma. plate current @ 1kv. In another paragraph it says to load the plate current to no less than 275 ma. for the reason specified, plate load impedance. So it seems to me that one would want to load a driver to the proper output designed into the rig. If you need less driving power then dissipate with the attenuator like Johnson built or build an exciter for the power level you need. Another approach I have seen is to feed the transmitter into a dummy load with a T connector and use the other T output to go the an amplifier input. The HT 32/37/44 are low power and can be used easily to drive an amp. They only give about 25 watts out which is about right for most amps. The bad thing about sloppy modulation from an exciter is that a Class A, AB or B amp will just amplify it and you really don't want that going out over the airwaves. Jim/W5JO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] Ranger driving SB220
I see this discussion every so often and wonder something. If you lower the plate voltage or current the final (s) draw, what is happening to the impedance the modulation transformer sees? The design of a class C final looks at the plate load impedance of the final. If you alter that, the modulation transformer sees another impedance and may not work properly. Some instruction manuals point this out in them. The manual for my Globe Champ says to load to 320 ma. plate current @ 1kv. In another paragraph it says to load the plate current to no less than 275 ma. for the reason specified, plate load impedance. So it seems to me that one would want to load a driver to the proper output designed into the rig. If you need less driving power then dissipate with the attenuator like Johnson built or build an exciter for the power level you need. Another approach I have seen is to feed the transmitter into a dummy load with a T connector and use the other T output to go the an amplifier input. The HT 32/37/44 are low power and can be used easily to drive an amp. They only give about 25 watts out which is about right for most amps. The bad thing about sloppy modulation from an exciter is that a Class A, AB or B amp will just amplify it and you really don't want that going out over the airwaves. Jim/W5JO Ron, Yes, the VKII uses a pair of 6146s and it has a 6AQ5 adjustable screen clamp tube. I see no reason to wast power with an attenuator and there is a sweet spot in the final current thru the mod iron that requires a less than full rated final current to avoid saturation. It seems to me that a fine adjust here would allow power reduction for use with an amp and also enable fine tuning the final current without reducing optimum drive current when used barefoot. Just an idea. I like the ability of the DSB transmitters like the HT 37, FT101,etc to lower the output power without having to retune the final. 73, __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] Using Heath SB 610 Monitor Scope tomonitor modulationonAM transmitter
Hi Geoff, It sure does pay to read ...the fine print, n'est ce pas...? Hi Hi ~73~ Eddy VE3CUI - VE3XZ * - Original Message - From: Geoff/W5OMR [EMAIL PROTECTED] To: Discussion of AM Radio in the Amateur Service amradio@mailman.qth.net Sent: Monday, February 11, 2008 10:18 PM Subject: Re: [AMRadio] Using Heath SB 610 Monitor Scope tomonitor modulationonAM transmitter Jim Wilhite wrote: To anyone considering an SB 610 or 614, keep in mind they must be constructed to match the IF frequency of the receiver to which they will be interfaced. Uh... I was under the impression that the 610 / 614 monitor scopes were for monitoring the 'transmitted' signal. Some of them were built to work with the Heath receivers with the 3 meg IF and those that were built for 455 Kc. had the coils that would do so. If you find one for with the 3 Kc IF coils, kc? you said 3meg(sic). Which is it? it won't work properly with a NC 300 or NC 183D for example. Heath packaged the coils for both with the units and the builder chose which he wanted. I doubt you will receive the coils that were not used during construction. Check them out before you find you have something that won't work with your receiver. So... I was under the impression that the 610 / 614 monitor scopes were for monitoring the 'transmitted' signal. Since I wasn't sure, I went looking. http://web.comhem.se/~u87540545/Heathkit/Products/pageSB610.htm Heathkit SB-610 The Heathkit SB-610 monitor scope is primarily designed for monitor the RF-signals, on-the-air signals, from the local transmitter. It can also be used to monitor received signals when connected to a receiver. It monitors RF-envelop, RF-trapezoid and RTTY pattern. SB-610 has also a built-in two-tone sinewave AF-oscillator for SSB-transmitter adjustment. The Monitor-Scope matches the SB-line. -- Driving your AM Rig without a scope, is like driving your car at night, without headlights. (K4KYV) -- 73 = Best Regards, -Geoff/W5OMR __ Our Main Website: http://www.amfone.net AMRadio mailing list List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
