Topband: BCI
I've been plagued by a problem I have finally identified but now need help in resolving. I thought it was birdies but realized it had an external component when I removed my antennas and they went away. I'm in a location where I can't put up a tower but have made extensive use of wires in trees and use my 160M Inv-L for 160, 20, 15, 12 10 meters. the 80M mostly vertical wire also serves for 80, 17, and 12 meters. I have been hearing birdies on 18 meters for a long time but recently I bought a P3 to fit the K3 and now can see much more than my alone ears noticed before. I only used CW and never listened to the signals and only bypassed them. When I had the 160M ant in line switched to 18M, I saw lines 5KHz apart on the P3. Usually I only have the 80M antenna in-line on 17M so this was a real discovery for me. Seeing that the interference was audio I listenbed on AM could hear audio which using the 80M ant narrow CW filters, I never had before. With the 160M antenna what used to be an irritation was now overwhelming interference to reception. And what I thought were birdies were the centers of the carrier on regularly spaced narrow AM signals generated in the circuitry. One station was an AM station from Puerto Rico and the other I never did listen long enough to, to hear the call but was stateside. Switching in the 80M antenna makes the lines on the P3 far less aggressive and switching to a 30M vertical, I see no lines whatsoever. I took two waterfall screenshots from the P3 and birdie1.jpg is showing 11KHz on each side of center and birdie2.jpg shows 100KHz on each side of center. Each line is 5 KHz. http://doctorgary.net/birdie1.jpg http://doctorgary.net/birdie2.jpg These are the worst on the transmit antenna but also am hearing them to a lesser extent on the HI-Z Triangular antennas as well. It seems like I should have a filter in line to block the BCB signals but then that would block 160 signals as well. I use the HI-Z for lowband work and certainly don't want to block those signals the same goes if I put a filter in the coax for my transmit antenna. Any suggestions of some kind of filter so I can get rid of these? Gary KA1J --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: BCI chase update
On 01/08/2012 04:46 PM, Lee K7TJR wrote: Paul you might want to be careful just shorting the receiver input. This would also put a short on the output of your preamp. This would have the preamp blasted with RF from your TX while trying to feed a short. My guess would be you could destroy preamps doing this. Clarification: Actually what I had in mind was to place the short at the input of the preamp. I want the preamp protected too. My only concern is the preamp might want to oscillate with a short on its input. I don't know whether these low frequency, medium gain preamps are prone to that or whether it would harm anything if they did oscillate. The 25+ dB gain, very low noise figure VHF/UHF preamps I am more used to can get pretty squirrelly with something other than 50 ohms on the input. 73, Paul N1BUG ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: BCI chase update
Why not use a DPDT relay as a bypass... This would allow the antenna side to be shorted to ground and the preamp input to be terminated into 50 or 75 ohms via a resistor, or in the other position the preamp would be connected to the antenna. Essentially the relay would be wired the same way as an in/out setup to switch an attenuator in/out of the signal path. Just a thought... -Bill KB8WYP Clarification: Actually what I had in mind was to place the short at the input of the preamp. I want the preamp protected too. My only concern is the preamp might want to oscillate with a short on its input. I don't know whether these low frequency, medium gain preamps are prone to that or whether it would harm anything if they did oscillate. The 25+ dB gain, very low noise figure VHF/UHF preamps I am more used to can get pretty squirrelly with something other than 50 ohms on the input. 73, Paul N1BUG ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: BCI chase update
N1BUG wrote: oscillate. The 25+ dB gain, very low noise figure VHF/UHF preamps I am more used to can get pretty squirrelly with something other than 50 ohms on the input. 73, Paul N1BUG On low bands, I routinely put a small (IE 10 pF) capacitor across the input of RF gain blocks to kill the bandwidth and prevent high frequency oscillations. With this in place, they should be fine with a short even if the short is somewhat inductive at VHF. Rick N6RK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Topband: BCI chase update
Prompted by Roger, N1RJ, I decided to do some digging around. Aided by isolating specific stages of my receive signal path as much as possible, and using precision 3 and 6 dB pads at various points to see where they dropped the IMD more than the attenuation of the pad(s), I have come up with a list of suspects. 1) The preamp. This was oversight on my part. A review of the original construction article clearly states a filter will likely be required if using a Beverage. Evidence: I simplified the signal path to BeveragePreampReceiver. Placing a 6 dB pad before the preamp dropped the IMD level more than 12 dB (may be closer to 18, I did not attempt to verify). Placing the 6 dB pad after the preamp dropped the IMD products 6 dB. 2) The ICE 196 receiver protector. Evidence: 6 dB pad before the 196 reduced IMD more than 12 dB. Placing the pad after the 196 reduced IMD 6 dB. Bypassing the 196 reduced IMD more than 12 dB. 3) A relay used to switch the preamp in and out. This relay had apparently failed, since replacing it with another of the same type made a big difference. This likely explains why my IMD problem when using the preamp went from annoying to severe a couple years ago. (I am aware relays in a receive signal path can be problematic due to insufficient current to clean the contacts). Based on results of this investigation my proposed plan (once I figure out how to fund it) is: 1) Replace the preamp. I'm not in the mood to build another one from scratch so I'm leaning heavily toward the Clifton Labs Z10040B. 2) Use a HPF in front of the preamp. Whether actually necessary or not it seems like good practice. I am leaning toward the Clifton Labs Z10022A, although I am torn between that and the Par Electronics BCST-HPF. The latter has more attenuation at the high end of the BC band, but not as much at the middle and low end. 3) Get rid of the ICE 196. I've had it with these things. This is not the first problem I have had with these devices generating crud. I have not as yet come up with a plan I am entirely comfortable with for receiver protection in its absence but I am leaning toward using a relay to short the receive signal path to ground when transmitting. Rather than put an additional relay contact in series with the signal path, I am thinking about having a normally open contact connected to the signal path, taking it to ground when transmitting. I welcome any comments. 73, Paul N1BUG ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: BCI chase update
Hi Paul: I have tried and tested many commercial and homebrew preamps for use on the TopBand (including those you talk about below). Although all of the preamps work - some work better than others. The W8JI design (that DX Engineering sells) has the best noise figure and overload handling capability of any that were measured. The highest performance from this preamp is achieved with a 18 VDC power source. I use this pre amp exclusively with my TopBand RX antennas. http://www.dxengineering.com/Parts.asp?ID=210PLID=107SecID=32DeptID=12Pa rtNo=DXE-RPA-1 A you mention in your paragraph 3 - To protect front ends - the KD9SV front end saver works very well. It does exactly what you described in a nice neat box. http://johnjeanantiqueradio.com/gary.htm 73! Tim K3LR -Original Message- From: topband-boun...@contesting.com [mailto:topband-boun...@contesting.com] On Behalf Of N1BUG Sent: Sunday, January 08, 2012 11:46 AM To: Topband Subject: Topband: BCI chase update Prompted by Roger, N1RJ, I decided to do some digging around. Aided by isolating specific stages of my receive signal path as much as possible, and using precision 3 and 6 dB pads at various points to see where they dropped the IMD more than the attenuation of the pad(s), I have come up with a list of suspects. 1) The preamp. This was oversight on my part. A review of the original construction article clearly states a filter will likely be required if using a Beverage. Evidence: I simplified the signal path to BeveragePreampReceiver. Placing a 6 dB pad before the preamp dropped the IMD level more than 12 dB (may be closer to 18, I did not attempt to verify). Placing the 6 dB pad after the preamp dropped the IMD products 6 dB. 2) The ICE 196 receiver protector. Evidence: 6 dB pad before the 196 reduced IMD more than 12 dB. Placing the pad after the 196 reduced IMD 6 dB. Bypassing the 196 reduced IMD more than 12 dB. 3) A relay used to switch the preamp in and out. This relay had apparently failed, since replacing it with another of the same type made a big difference. This likely explains why my IMD problem when using the preamp went from annoying to severe a couple years ago. (I am aware relays in a receive signal path can be problematic due to insufficient current to clean the contacts). Based on results of this investigation my proposed plan (once I figure out how to fund it) is: 1) Replace the preamp. I'm not in the mood to build another one from scratch so I'm leaning heavily toward the Clifton Labs Z10040B. 2) Use a HPF in front of the preamp. Whether actually necessary or not it seems like good practice. I am leaning toward the Clifton Labs Z10022A, although I am torn between that and the Par Electronics BCST-HPF. The latter has more attenuation at the high end of the BC band, but not as much at the middle and low end. 3) Get rid of the ICE 196. I've had it with these things. This is not the first problem I have had with these devices generating crud. I have not as yet come up with a plan I am entirely comfortable with for receiver protection in its absence but I am leaning toward using a relay to short the receive signal path to ground when transmitting. Rather than put an additional relay contact in series with the signal path, I am thinking about having a normally open contact connected to the signal path, taking it to ground when transmitting. I welcome any comments. 73, Paul N1BUG ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Topband: BCI chase update
Paul you might want to be careful just shorting the receiver input. This would also put a short on the output of your preamp. This would have the preamp blasted with RF from your TX while trying to feed a short. My guess would be you could destroy preamps doing this. Lee K7TJR OR ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: BCI chase update
Paul, I will agree with Lee. I think the best would be to use a small relay that would open the antenna on transmit and also short it to GND. Nothing touching the Pre-Amp. All Electronics have some very nice DIP relays that will do the job. I have no connection with All Electronics, Just a good supplier. 73 W0RI Paul you might want to be careful just shorting the receiver input. This would also put a short on the output of your preamp. This would have the preamp blasted with RF from your TX while trying to feed a short. My guess would be you could destroy preamps doing this. Lee K7TJR OR ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Topband: BCI
A strange happening already this season, I am hearing WTVN-AM 610 khz (Columbus OH) plain as day on 1830 khz. This is the only frequency that I hear it on. I am at least 35 miles from this station, and it is west of me. The antenna is a 350 ft long East-West bi-directional beverage. I just moved this antenna away from transmit antenna to the south and added a frontend protector on my FT-920. That's the only thing that has been changed to this antenna. I don't hear either of our local stations WHTH-AM 790 khz or WCLT-AM 1430 khz. WCLT is less than one air mile from me. What do guys use to smash the BCI? Thanks for reading. Scott, K8SM ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: BCI
On 12/13/2011 05:36 PM, Scott Long wrote: A strange happening already this season, I am hearing WTVN-AM 610 khz (Columbus OH) plain as day on 1830 khz. This is the only frequency that I hear it on. I am at least 35 miles from this station, and it is west of me. Wouldn't be the first time an MW station puts out a signal on a harmonic frequency. This happens all the time. If you tune around between 2 and 3 MHz, you will often find a handful of broadcast harmonics. Some come and go, others are more permanent (like 2730 kHz). The way to get them fixed is to notify the station and get them to fix the problem. If they don't, notify the FCC... -- All rights reversed. ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: BCI
From personal experience, WTVN-AM has had third harmonic issues going back as far as 35 years. Remove your receive protector and check other antennas to be sure the harmonic is still there. Also turn on the attenuator in your rig and notice if the decrease in the harmonic is the same at the amount of attenuator or if the drop is much more than the attenuator. If all the tests (alternative antenna, attenuator) show it is a harmonic, call the station and ask to speak to the Chief Engineer. If the station gives you the run-around, call and/or write the FCC. They have a history of issues ... 73, ... Joe, W4TV On 12/13/2011 5:36 PM, Scott Long wrote: A strange happening already this season, I am hearing WTVN-AM 610 khz (Columbus OH) plain as day on 1830 khz. This is the only frequency that I hear it on. I am at least 35 miles from this station, and it is west of me. The antenna is a 350 ft long East-West bi-directional beverage. I just moved this antenna away from transmit antenna to the south and added a frontend protector on my FT-920. That's the only thing that has been changed to this antenna. I don't hear either of our local stations WHTH-AM 790 khz or WCLT-AM 1430 khz. WCLT is less than one air mile from me. What do guys use to smash the BCI? Thanks for reading. Scott, K8SM ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
