KiwiSDR (http://kiwisdr-m0kwr.ddns.net:8073) I am very impressed with the performance of the KiwiSDR.Although I was still suffering from overload from a nearby AM transmitter. I have installed a high pass filter in the antenna line just before the switch box and reduced the overloading to an acceptable level.
High Pass Filter.
All photo's © 2003-2018 Kent Royce. Copyright Kent Royce 2018
My antennas are always changing when I wrote this I only had 2 antennas.
A 220 ft inverted V doublet @ 40ft for all bands and a 160 meter inverted L as my main 160 meter antenna.
My 220 foot doublet makes receiving on the 160 meter band almost unworkable for weak signals but this loop has made all the difference right through the HF bands. The loop provides good coverage from 10 Khz to 30 Mhz. I owned a Welbrook Loop but it only lasted about 9 months before it failed. RF probably caused the failure.
Front End Saver.
When you have a receive loop or mini whip or any other receive only antenna for that matter you want to make sure you don't transmit RF into your receiving antenna and then into your radio causing expensive damage to your radio. This is a serious thing to consider when you install any receive antennas.
This perfect solution was designed years ago by Gary, KD9SV.
To avoid this problem some form of switching is required to stop RF getting into your radio or receiver. Some radios are equiped with a dedicated receiver antenna socket but I prefer to go one step further.
A good protection circuit to eliminate the possibility of blowing your receiver's front-end while using these auxiliary receive antennas specially on low bands.
I was discussing this RF problem with a local Radio amateur G8EQY who has facilities to hand to produce the circuit board for this project. The following week Scott gave me the finished and built circuit board ready for testing. Totally unexpected and an amazing quality job. See the pictures of Scottís completed project. The relays used are HJR1-2C L-12V DC which have an operate/release time: 6/4ms and these work very well.
OK so what does it do? In simple terms it disables your receiver antenna before switching your transmitter to TX. Connect your foot switch or TX button to the box/panel then connect your transmitter PTT line to the box. The coax through the box is cutting off your receive antenna before your transmitter goes into transmit. I use this to protect my Kiwi-SDR and my IC7700. My FT2000D, TS2000 and Icom IC7700 have a receive antenna sockets but i still use this added protection. All my transmitters are connected through the box and one PTT button is in use.
Due to ever increasing noise on our HF bands I have been looking for alternative ways of reducing the pain of all this disturbing interference.
Scott (G8EQY) made a couple of these Wellgood (M1GEO) loop amplifiers to see if they were as good as my original Wellbrook Loop. I found Scotts loop much better with a lower noise floor.
I have been using Scottís version of the wide aperture Welbrook loop for the past year and itís been working great. I can't say the same for the Wellbrook Loop though. The Wellbrook Loop died after 9 months months. I put Scott's loop up in the usual dimond configuration on a cheap rotator at about 6 feet off the ground. I used a radom peice of wire 8 meters long. This worked great but i needed to keep rotating the loop to pick up weak signals.
After a few months I started doing a bit of internet research on loops and different shapes and I decided to try a double loop.
I connected 12 meters of cheap multi strand wire in a double loop configuration. I connected this to the amplifier at the bottom. See picture below. This configuration still allows you to null out a local noise source but gives you a improved sky wave reception.
Some really interesting loop information on this site. The Welbrook Loop exposed.
George Smart - M1GEO
Wide band Active receive loop
SDR receive antenna is connected to a Kiwi SDR