Re: Topband: DX Engineering Preselector
Why do you feel it is the best? Without knowing the circuit of the limiter I can just surmise that it uses diodes or other non linear device to clip the input above a certain level. Try it ahead of the preselector where the signal levels are less. Carl KM1H - Original Message - From: John Harden jh...@bellsouth.net To: topband@contesting.com Sent: Friday, August 24, 2012 3:44 PM Subject: Topband: DX Engineering Preselector I just put in the above as it is the best one out there... However, when I put in the Array Solutions RF Limiter/Arrestor between the preselector and the K3 I get distortion in the signals. Any comments out there? The RX antenna is a Hi-Z 8-Circle array. 73, John, W4NU ___ UR RST IS ... ... ..9 QSB QSB - hw? BK - No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1424 / Virus Database: 2437/5220 - Release Date: 08/23/12 ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: DX Engineering Preselector
I understand the process quite well but I dont understand the need for such a device on a Beverage the large majority of the time. The only time Ive used a preamp is on those quietest of nights where only 9-10dB of gain from a preamp with a 1.5dB NF brings a ghost of a signal out of the noise. I didnt have to buy it either as I have the equipment to design, build, and test to my own stations needs. And not a generic catalog item such as the RPA-1 which amplifies everything from LF to VHF and dumps it all into your receiver including everything from the BCB. No wonder it and the limiter are overloaded. The rather generous specs are for a single signal only, not thousands of them. At the very least you should have a 160M bandpass filter, or a BCB filter if you dont want to bother switching individual filters per band, ahead of the RPA-1. Note also the instructions include methods to reduce gain, not all of which I agree with. Carl KM1H - Original Message - From: John Harden jh...@bellsouth.net To: ZR z...@jeremy.mv.com; topband@contesting.com; Richard Jaeger k4...@mindspring.com Sent: Friday, August 24, 2012 4:47 PM Subject: Re: Topband: DX Engineering Preselector Carl, I bought the DX Engineering device because it has the best third order intercept. Just see W8JI's web site. Tom has a chart that compares TOI's for various devices. I trust his meaurements because they are based on facts and knowledge of the RF arena. They are not opinions and assertions as one hears often on the reflector... When comparing receivers it tells us how well devices separate two closely placed signals. As you know it is a calculated value based on the plot of Output power in dBm vs. Input power in dBm. It cannot be measured like selectivity. The IP3 really tells us how well two signals 3-5 kHz apart can be copied. Tom's values are good enough for me. This device replaces an ICE 160 only receive preamplifier. 73, John, W4NU K4JAG (1959 to 1998) On 8/24/2012 4:19 PM, ZR wrote: Why do you feel it is the best? Without knowing the circuit of the limiter I can just surmise that it uses diodes or other non linear device to clip the input above a certain level. Try it ahead of the preselector where the signal levels are less. Carl KM1H - Original Message - From: John Harden jh...@bellsouth.net To: topband@contesting.com Sent: Friday, August 24, 2012 3:44 PM Subject: Topband: DX Engineering Preselector I just put in the above as it is the best one out there... However, when I put in the Array Solutions RF Limiter/Arrestor between the preselector and the K3 I get distortion in the signals. Any comments out there? The RX antenna is a Hi-Z 8-Circle array. 73, John, W4NU ___ UR RST IS ... ... ..9 QSB QSB - hw? BK - No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1424 / Virus Database: 2437/5220 - Release Date: 08/23/12 - No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1424 / Virus Database: 2437/5220 - Release Date: 08/23/12 ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Topband: PREAMP/PRESELECTOR
Most Beverages don't require a preamp of any type, in my estimation. The shorter ones may need a bit of a boost but those over 500 ft seem to do quite nicely on their own most of the time. If you do believe that some amplification is necessary then 6-10 db is about all that you should consider using lest you overwhelm your front end and introduce more noise and garbage. Now, IF you need a bit of a boost, consider killing two stones with one bird. If you have a need to eliminate some noise, the MFJ 1025/1026 noise reducers have a bit of a preamp built in. It is just a few db but it might suffice. When I need just a bit of amplification I use the preamp built into my radios (PRO2 and K3). The preamps in both these radios appear to do a good job in my application (though I have no real idea what the REAL noise figure is). For loops and other RX antennas whose gain is -12db and beyond, an external 10-20db amplifier is desireable and there are a lot of choices out there, from the simple but effective W7IUV and KD9SV designs ( both of which I have built and use) to the more exotic designs by the likes of W8JI. I am referring only to amplification above. If you require selectivity in front of the RX antenna for any reason then that is a completely different situation and one of the commercially manufactured preamps with tuned input is desireable. IMHO anyhow. Bill VE3CSK - No virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.2197 / Virus Database: 2437/5223 - Release Date: 08/25/12 ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: DX Engineering Preselector
All of this obscures the real issue. The real issue is a device that uses back-to-back diodes to limit signals has soft limiting that starts well below the clamp voltage. If the advertised clamping voltage is .3 volts, that is in the negative dBm range. Most receivers are far into the positive dBm range, so the addition of a device like that would just kill the system dynamics. Still.. I understand the process quite well but I dont understand the need for such a device on a Beverage the large majority of the time. The only time Ive used a preamp is on those quietest of nights where only 9-10dB of gain from a preamp with a 1.5dB NF brings a ghost of a signal out of the noise. He clearly said he has an 8 circle array, not a Beverage. The gain of an 8 circle is highly dependent on element spacing. As a matter of fact, what the manufacturer sets as sensitivity threshold really controls how small the array can be. It's all about destructive phase in the forward direction, which gets worse and worse with close spacing. I didnt have to buy it either as I have the equipment to design, build, and test to my own stations needs. :-) And not a generic catalog item such as the RPA-1 which amplifies everything from LF to VHF and dumps it all into your receiver including everything from the BCB. No wonder it and the limiter are overloaded. The rather generous specs are for a single signal only, not thousands of them. Actually, that isn't true. The IP3 test is NOT a single signal test. It is a pretty good test of multi-signal capacity. In any event, despite non-techical claims, someone would be hard pressed to generate IMD in the amp in any condition where the amp really is needed. Because I have cable and splitting losses, I run them all the time on my system here (without pre-filters), although I do agree with a short feeder and a normal Beverage they probably are not required. But then he did say he had a different antennaand none of us know how sensitive it really is. :-) At the very least you should have a 160M bandpass filter, or a BCB filter if you dont want to bother switching individual filters per band, ahead of the RPA-1. Note also the instructions include methods to reduce gain, not all of which I agree with. The instructions are good. I would not run a bandpass filters ahead of that amp in any normal situation. We run multiple transmitters here on site, with NO pre-filtering, and the amplifiers are way down the list on limiting things in the system. As a matter of fact, we transmit while receiving on the same band without issue. We also sometimes have transmitters on multiple bands at the same time. If the amplifier is being hit with a very strong local BC signal it might be good to knock out the BC station, but the amplifier will handle far more than any receiver. Here is how his system stacks up: 1.) The limiter hard-limits in the negative dBm range, because it supposedly clamps at 0.3 volts. 2.) The early element amplifiers run about 10 dBm output TOI 3.) The Hi Z amp in the box is about 30 dBm TOI 4.) The DXE amp is about 45 dBm TOI. Is it any surprise he started having problems when the limiter was added? I haven't found a device yet with back-to-back diodes that does not ruin a system's dynamic range. This is because the diodes start to go non-linear resistance below the hard-clamping voltage, which is already far too low. 73 Tom ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: PREAMP/PRESELECTOR
Now, IF you need a bit of a boost, consider killing two stones with one bird. If you have a need to eliminate some noise, the MFJ 1025/1026 noise reducers have a bit of a preamp built in. It is just a few db but it might suffice. That is a mediocre TOI amplifier for a line driver or broadband booster application. It is a simple single J310 JFET source follower, and only makes about 5 -15 dBm TOI. That device also has pretty high noise floor because of gain distribution. It has a good bit of loss ahead of the 2N5109 output transistor. It also has a back-to-back diode clamp inside. It does the job it was intended to do pretty well, which is to mix a noise signal into a transmitting antenna's receive path, but I would not recommend it for amplification. By the way, if you match the emitter follower on the output to the receiver a bit better the gain and TOI will get a few dB better. It's pretty hard to quantify the TOI, because control settings and receiver impedance affects it, but someone is far better off using a real amplifier if needed. 73 Tom ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: DX Engineering Preselector
We used the DXE 8-circle without preamp and preselector last year at DR1D in M/S WWDX CW. In my opinion neither is necessary even with 200m of RG-6 feedline. I looks as that the RF limiter is causing your problem, is that using anti parallel diodes or just a light bulb + spark gap? With diodes you might try to add more diodes in series. 73 Peter, DJ7WW -Original Message- From: topband-boun...@contesting.com [mailto:topband-boun...@contesting.com] On Behalf Of John Harden Sent: Freitag, 24. August 2012 21:45 To: topband@contesting.com Subject: Topband: DX Engineering Preselector I just put in the above as it is the best one out there... However, when I put in the Array Solutions RF Limiter/Arrestor between the preselector and the K3 I get distortion in the signals. Any comments out there? The RX antenna is a Hi-Z 8-Circle array. 73, John, W4NU ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: [TowerTalk] How Do I Schedule a Freight Pick-Up?
On Sat, 25 Aug 2012 11:22:00 -0400 Larry lkn...@nc.rr.com writes: I did this several years ago (1984?). I assume the situation is the same now that when the truck shows up at your door with your tower YOU have to unload it. I was somewhat lucky and tied the tower (75 footer weighing about 800 lbs) to a tree and drove the truck out from underneath the tower. Part way through I hooked the tower balance point to an engine hoist and was able to move it around (I was on smooth concrete). What a PITA to have a tower or anything else delivered that way. I've specified, as part of the deal, that unloading must be providedno exceptions. If they can't, then use another service. 73, Charlie, N0TT 73, Larry W6NWS -Original Message- From: Bill Gaines Sent: Saturday, August 25, 2012 8:21 AM To: towert...@contesting.com Subject: [TowerTalk] How Do I Schedule a Freight Pick-Up? On June 29 my LM-470d was destroyed in a wind storm. I immediately started looking here and elsewhere for a suitable replacement. I found a couple but both were on the left coast and both indicated the buyer would have to arrange shipping. I have since found others closer to me but still the same thing about me doing the leg work on locating a shipper. I finally decided to replace the old tower with a new one also being shipped from the west coast. My reasoning was that since they do this full time they must have shippers waiting at their door to pick things up and haul away. I am told by the manufacturer that the tower is completed and is awaiting pick up by a trucking company. I have been told this story several times nowwaiting on a company to come to pick it up. My question is this. Where do I go to find a flat-bed truck that will pick this tower up in California and bring it to me in Ohio? There simply must be a reasonably quick way to get this done. Bill AD8P ___ ___ TowerTalk mailing list towert...@contesting.com com/mailman/listinfo/towertalk ___ ___ TowerTalk mailing list towert...@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
