This discussion of Hi Z amplifiers has been quite interesting. Excellent information from W1FV and K7TJR. I have an RX amp question, related but slightly off-topic. I have an MFJ-1025/1026 noise canc
The J310 is as quiet as they come. It has a 100 MHz noise figure of (only) 1.5 dB. 73 and aloha, Dave KH6AQ _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflect
Steve, The J310 is normally a pretty low noise device. Perhaps you should look at filtering the power supply and any control and feed cables. GL and 73, George, AA7JV I have an RX amp question, relat
Steve, Sorry, I did not directly answer you question. Look at the specs of the IF3602. (But also look at the price!) George AA7JV I have an RX amp question, related but slightly off-topic. I have an
Steve, Couple of questions to rule out gain distribution issues: 1) On the sense antenna input do you have the pre-amp turned on or off? 2) Is your sense antenna intrinsically inefficient like a beve
Author: John Kaufmann via Topband <topband@contesting.com>
Date: Sat, 14 Mar 2020 13:48:22 -0400
Steve, An alternative is to do the cancellation with all passive circuitry. You can find some designs on the Web but you'll have to build them yourself. An example (one that I built) is this one from
On 3/14/2020 10:20 AM, GEORGE WALLNER wrote: Steve, Sorry, I did not directly answer you question. Look at the specs of the IF3602. (But also look at the price!) George AA7JV JFET's have a channel re
Another pitfall that you have to be careful to avoid with the MFJ-1026 is making sure the level of the QRN you are trying null that is coming out of the sense antenna isn't much lower in amplitude th
Steve, I have an MFJ-1025, and I have never experienced your issues. I was going to ask some of these questions myself. I have had very good results indeed with mine for eliminating a single source o
Exactly! This is very important to get a deep noise null. Mike W0BTU _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Hi Mike, Yeah, when the off-air noise floor is a lot higher than the thermal noise floor from the JFET pre-amps, the imbalance I was alluding to wouldn't typically impact the overall noise floor sinc
The DXE NCC-1 and NCC-2 are well equipped to deal with this. I haven't measured noise, but I did carefully measure phase shift and gain for multiple settings. They're in http://k9yc.com/VE3DO.pdf 73,
Steve, I ran a SPICE model of the MFJ-1095 front end. What gain there is resides there. The next three stages have unity gain. The input noise is: 1.8 MHz, 50 nV/Hz^0.5 7.0 MHz, 26 nV/Hz^0.5 14 MHz,
Dave is that -112 dBm you calculated the output referred noise? If so, what is the gain behind it? Thanks, 73, Mike W4EF....... 1.8 MHz, 50 nV/Hz^0.5 7.0 MHz, 26 nV/Hz^0.5 14 MHz, 19 nV/Hz^0.5 28 MHz
I am trying to understand what these noise cancelling schemes do that couldn't be done with a simple loop (rotating the loop until the noise drops into one of the null directions). You can easily pro
I used one of these systems (homebrew WA1ION) for a couple of years in the early 2000s. My problem was a speed-controlled water pump (local water authority) very close to my QTH. The pump was in the
On 3/14/2020 3:17 PM, Richard (Rick) Karlquist wrote: I am trying to understand what these noise cancelling schemes do that couldn't be done with a simple loop (rotating the loop until the noise drop
Great explanation. Now I know what these canceling boxes are good for. I have a troublesome power pole about 100 ft off the corner of my property. I could put a sense antenna up in that corner and u
Hi Rick, A noise receiving antenna close to a noise source is used in conjunction with a higher performance receiving antenna such as a Beverage or an array of short verticals and a passive or active
A couple of issues I see. It depends which direction(s) the noise and desired signal are coming from. You may null the noise and signal. Also, the loop is bi-directional. I've been playing with a DX