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Folks, I built a couple of 49:1 unun transformers attached to a 130' wire. Amazing of how well this works. Primary has 2 bifilar turns, and secondary is total of 14 turns. Some great references out there such as https://elginradio.wordpress.com/2017/10/17/end-fed-half-wave-antennas/ The...

Folks, Playing around with building a VHF Class C amplifier and using this schematic as a baseline http://electronics-diy.com/1W_Universal_RF_Amplifier.php After building this per the schematic, I'm not getting any gain! If I add some biasing to the base of the transistor with a 20K...

Folks, Thanks on the other threads the suggestions for identifying and eliminating various RFI across various HF bands. I've significantly reduced my noise, especially with the use of mix 31 and mix 43 toroid chokes around problematic cables. Some really noisy switchers, I've replaced, etc...

Folks, On another thread, we discussed the value of toroid chokes for HF to reduce noise and to eliminate common mode currents. Especially for low band and HF using a mix 31 and mix 43, I noticed a HUGE improvement with noise. What about for VHF/UHF? Do any of you use a choke on any of your...

Folks, I'm scratching my head here and maybe you can help me out. I noticed today that I dropped by noise by at least S3 on the meter for 80/40meters by disconnecting the other 2 radios (VHF & UHF) that are connected to the same face plate/cover plate on the wall. See the attached picture. Its...

I know lots of folks hate this antenna. But I was really shocked today when I was comparing the CHA-250B to that of my ATA120A screwdriver antenna on my truck and trying to access a 6M repeater north of me. My truck with the ATAS could hit the repeater just fine with about S9 and full...

So, I know I've got other threads somewhat related to RFI - or at least antenna issues and trying to deal with related RFI issues. But, I took some time this afternoon to shut down the breakers and run the radio on battery power to see what I have for on-premise noise and what is off-premise...

Folks, I'm thinking now to get away from all the noise sources in the house, that I need to get the antenna as far away from the house as possible. That being said, because of retaining walls in the way, I want to go overhead with LMR-400 cable from the house roof eave to a Pressure treated...

Folks, I was doing some testing of a CHA-250B. I know some of you will call it a dummy load and not a good antenna; but lets put that aside and consider the performance difference I'm seeing in two locations. Initially I had it about 30' from the house near the ground attached to a metal fence...

Folks, Hope all is well. Just getting started in HF after a long hiatus. Back in my old place, I used a simple vertical (A99) for 10 meters back when conditions were good (~30 years ago). But I lived in a flat area with a clear view of the horizon. I did pretty good with causal DX. Now, I...

Folks, I just put an Anytone 5888 on the bench to do a test and saw an interesting observation. I just tested UHF / 440 for 12dB SINAD, and I'm seeing around -117dBm. What is weird, is if I move the selected VFO over so my SINAD test is on the 'inactive' side (just monitoring side), I gain...

Folks, I noticed this past week that I blew out the front end of my XM/Siruis receiver in my truck. It might be just coincidence, but by 2m/70cm antenna is only a few feet away from the XM radio receiver. Has anyone experienced this? Since XM is up in the 2GHz range, I wouldn't have thought...

Folks, Couple of questions and I was hoping someone had some experience in this area they could share. First off, I would like to use two (maybe a 3rd) antennas with a single feedline. I see a ton of diplexer's and triplexers out there at a reasonable cost. The only concern I have is that most...

Folks, I have an MFJ VHF/UHF SWR/Watt Meter (MFJ-842). Lately the forward and reflect needle has not been at zero when its unplugged. Haven't dropped it or anything. Is this a known issue? Any way to correct? Thanks, -J

Hello All, Just thought I'd post this since I've seen many posts in the past, sometimes with incorrect information. Generally for light duty repeaters, I use some Motorola mobiles that have been modified for better cooling. But for the link radio (linking to a hub repeater), the LPI Motorola's...

Hello all, I know several threads have discussed issues with using mobile radios (such as the Maxtrac/Radius) for repeater usage because of their designed duty cycle. Besides adding forced air cooling with fans, has anyone tired extending the cooling fins with aluminum using a thermal adhesive...

Over the past few months I've been reading various duplexer designs and one that I can't wrap my head around is the single loop bandpass/reject cavity. I get the dual loop where the cavity is tuned to be resonant at the bandpass and the Capacitor is tuned to the reject. But the single loop I...

Folks, I have a Motorola Maxtrac with very low audio on MIC pin 8. I'm going to review the schematic to see if I can figure it out, but thought I'd reach out to you all and see if there is a common (or well known) issue I should be aware of. The audio to the internal speaker is just...

Hello folks, I've read through the Repeater Builder Dot Com site on duplexers both bandpass and notch filter designs. And even though there is the poor man's way of tuning listed, I was wondering about a different approach. Most of us don't have a service monitor or a scope that can go up to...

Hello all, Just a curiosity question here. Why do most repeaters only use an RX PL code and not BOTH an RX and TX PL code? The reason I ask, it seems like it would clean things up with some of us using multi-band radios which can be more prone to intermod...and our RX wouldn't come...