This has been a very interesting thread - Thanks for all the input. Perhaps I have set my expectations too high. A typical application is on 15 meters, late in the opening, working JA's from here in
Depending on the exact circuit and device, to measure noise from the device itself, dont you have to terminate the inputs to put the normal impedance on them? The circuits are often designed with the
I did that - terminated in 50 ohms. 73, Steve, N2IC 73, Guy K2AV This has been a very interesting thread - Thanks for all the input. Perhaps I have set my expectations too high. A typical application
Possibly static, nearby lightning, or high levels of TX RF may have damaged one or more of the semiconductors in your MFJ-1025. --Original Message-- From: Topband [mailto:topband-bounces+lloydberg=td
Steve, I performed a hand calculation of the MFJ-1025 14 MHz noise and it's (only) 9 nV/Hz^0.5, or 0.2 uV in 500 Hz. This is -120 dBm, or S-1. But you measure S-4 noise. What is going on? Questions t
Dont forget there is gain in the signal paths. That first AUX input stage is a Norton configuration amp with gain controlled by the unknown transformer ratios. The two J-310's that sum the signals al
Circuit gain is accounted for in my calculations. I ran a sim of the input amp and could get it to work with gains from 0.5 to 2 using different transformer ratios. So, I think the gain-of-2 I used i
Hi Dave, In my experience that is not a typical Norton amplifier gain . Most would be considerably in excess of that at 11 or 19 dB. They can run from 5 to 19 dB or so but what would be the purpose o
I just happen to have a spare MFJ-1026 at home. I did a real quick test using my FT1000MP MK-V while powering the MFJ-1026 from an Astron supply. Similar to your results, Steve, I got about a 12 to 1
I remember having some experience with that MFJ-1026 a number of years ago and found the trade off of increased noise floor vs cancelling not worth the effort. Trading one evil for another evil. Obvi
Mike, thank and these are great data points you've provided. Questions: Was the MFJ-1026 PHASE control set near zero? That could account for the low AUX gain. *Mike's data* FT1000MP MK-V Main Antenna
Tom Rauch, W8JI has a nice webpage dedicated to the MFJ-1025/1026 at https://www.w8ji.com/mfj-1025_1026.htm. A few relevant excerpts follow. "The only drawback of the higher noise floor of the MFJ-10
Mike, is there any reason why you tested it above 20 MHz? That's outside the 1026's specified frequency range. 73, Mike W0BTU _________________ Searchable Archives: http://www.contesting.com/_topband
Having just read some of these posts, I just did a few tests on my MFJ-1025. (bought mine second-hand very cheap - a lot of people buy these thinking they will get rid of any noise!) I modified it to
In my tests of my NCC-1, I found it pretty useless above 40M. It accommodates optional preamps; it's driven by a K9AY 8x4 matrix switcher, which includes his preamps (switchable). 73, Jim K9YC ______
Another good advantage to the electronic schemes is that you don't have to go outside to rotate them when the noise that's bothering you is coming from a different direction. 73, Jim That is an inter
Roger, I didn't realize that the 1025 (which is what I have) didn't have a preamp on the auxiliary (noise) antenna input! I chose the 1025 over the 1026 because I did not want the small whip antenna,
Hi Mike As I said in my previous post, as the 1025 uses the same PCB as the 1026, I effectively modified my 1025 to become a 1026, using MFJ's circuit, built on to the empty slots on the PCB. And as
You were spot on, Dave. Thanks for the suggestion. I rechecked the numbers this morning and the AUX (i.e. sense antenna path) gain varies about 2dB as a function of where the phase control is set. It