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 noise canceller.
A small loop antenna provides a mechanically steerable null off of
On 3/14/2020 3:27 PM, Greg - ZL3IX wrote:
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 same
direction as most of the wanted DX, so a
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 drops into one of
the null directions).
I can't find the very recent email where this example was
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 same
direction as most of the wanted DX, so a nulling loop didn't work.
What I did was to
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 prove to yourself
with a hand held AM BCB receiver equipped with a ferrite
bar antenna that even
Dave is that -112 dBm you calculated the output referred noise? If so,
what is the gain behind it?
Thanks,
73, Mike W4EF...
On 3/14/2020 2:13 PM, Dave Cuthbert wrote:
Steve, I ran a SPICE model of the MFJ-1095 front end. What gain there is
resides there. The next three stages have unity
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, 19 nV/Hz^0.5
28 MHz, 13 nV/Hz^0.5
Depending on the input stage gain (I'm modeling 1 to 2
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, Jim K9YC
On 3/14/2020 11:54 AM, Michael Tope wrote:
Another pitfall that you have to be
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 since that is still
limited by off-air noise. In Steve's particular case, aside from one
S3-to-S4
Exactly! This is very important to get a deep noise null.
Mike W0BTU
On Sat, Mar 14, 2020, 1:55 PM Michael Tope wrote:
> 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
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 of RFI. Something at your end is not right.
Mike,
There have been cases where my 580' Beverage
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 than what is
coming out of the main TX antenna (I am talking about levels measured
directly 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 resistance that has thermal
noise like any other resistor. That sets the
noise voltage for
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 WA1ION:
https://www.pa4tim.nl/wp-content/uploads/2011/02/passive_bb_phasing.pdf.
The drawback to
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 beverage or
K9AY loop or is it something efficient like a tribander up reasonably high?
3) Is your
Steve,
Sorry, I did not directly answer you question. Look at the specs of the
IF3602. (But also look at the price!)
George
AA7JV
On Sat, 14 Mar 2020 10:40:30 -0600
n2ica...@gmail.com wrote:
This discussion of Hi Z amplifiers has been quite interesting. Excellent
information from W1FV and
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
On Sat, 14 Mar 2020 10:40:30 -0600
n2ica...@gmail.com wrote:
This discussion of Hi Z amplifiers has been quite interesting.
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
On Sat, Mar 14, 2020 at 6:40 AM wrote:
> This discussion of Hi Z amplifiers has been quite interesting. Excellent
> information from W1FV and K7TJR.
>
> I have an RX amp question,
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 canceler. I like to use it on the higher HF bands
to cancel power line QRN. The noise is typically
More power to make up for my 10db excess noise = xxx Kw - whoopee! Need
to get some 3 phase.
Remote Rx, eg 100km makes a lot more sense. Clubs could put up shared
facilities.
With direct sampling synchronous receivers and down sampling of say the
bottom 50Khz of 160, every user could
I'll put my tongue in the other cheek and ask how me increasing my TX power
improves the SNR on a received DX signal?
Wes N7WS
On 3/14/2020 4:20 AM, Rob Atkinson wrote:
This is only half tongue-in-cheek.
With the ambient noise going up, and there being limits to the size and cost of
another superb article, Jim. tnx!
73, w5xz, dan
On Friday, March 13, 2020, 01:52:39 PM CDT, Jim Brown
wrote:
On 3/13/2020 11:13 AM, Mikek wrote:
> advice about common mode filtering,
This ran in National Contest Journal a year or two ago.
http://k9yc.com/RXChokesTransformers.pdf
George, Thank you for that amazing video. Fred KB4QZH
Original message From: GEORGE WALLNER
Date: 3/14/20 12:25 AM (GMT-05:00) To: Mike Waters ,
topband@contesting.com Subject: Re: Topband: Misek/Lankford Phaser 2 Project I
have built and tested Langford's Phased Delta Flag
>This is only half tongue-in-cheek.
>With the ambient noise going up, and there being limits to the size and cost
>of receiving arrays most amateurs can build, the next logical step is to raise
>the output power. Perhaps the FCC should be >petitioned to raise the legal
>limit? They were
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