Hi
any good suggestion how to reduce noise from VHF TX on receiving on UHF fo RS44
I'm using two antenna antena 8meters away each other but is hard to hear anything when TX.
73 Andy
Hello Andy,
The issue is the third harmonic of the 2M uplink being "heard" by a sensitive receiver setup on 70cm. Here is a link from our old friend Tony, AA2TX (SK), that is still applicable today.
The idea is to filter! It may take something on the transmit side and the receive side, depending on your station. Too many variables--but this will let you begin to work towards reducing the problem.
https://www.amsat.org/a-simple-desense-filter-for-mode-j-satellites/
There are also some nice bandpass filters that can be used, but they are a good bit more expensive.
73, Mark N8MH
On Sun, May 24, 2020 at 5:16 AM Andy Brian via AMSAT-BB amsat-bb@amsat.org wrote:
Hi
any good suggestion how to reduce noise from VHF TX on receiving on UHF fo RS44
I'm using two antenna antena 8meters away each other but is hard to hear anything when TX.
73 Andy _______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
Hoi,
Instead of putting a diplexer as filter( best is to use 1 per band), if you have the possibilty to make stuff your own, just 'split' a diplexer by making an LPF (low pass filter) at the 2m antenne and a HPF ( high pass filter) at the 70cm antenne. Or find some to buy (MINI CIRCUITS maybe?). This way you have a filter at both antennas. Mostly a diplexer is used only on one antenna, while the other diplexer port is closed with a small dummy load. Keep in mind the tx-pwr!
Best 73's
Jerry,ON4CJQ
----- Oorspronkelijk bericht ----- Van: "amsat-bb" amsat-bb@amsat.org Aan: "amsat-bb" amsat-bb@amsat.org Verzonden: Zondag 24 mei 2020 11:14:51 Onderwerp: [amsat-bb] RS-44 VU noise from TX
Hi
any good suggestion how to reduce noise from VHF TX on receiving on UHF fo RS44
I'm using two antenna antena 8meters away each other but is hard to hear anything when TX.
73 Andy _______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
On 05/24/20 13:43, Jerry via AMSAT-BB wrote:
Instead of putting a diplexer as filter( best is to use 1 per band), if you have the possibilty to make stuff your own, just 'split' a diplexer by making an LPF (low pass filter) at the 2m antenne and a HPF ( high pass filter) at the 70cm antenne. Or find some to buy (MINI CIRCUITS maybe?).
I have been eyeing the "144 MHz 5 Pole Low Pass Filter for > 0.75 KW built by DL2FCN" on this page:
http://dg7ybn.de/technical/Filters.htm
There is just enough build detail to try constructing my own. I plan to test it with the nanoVNA (v1) and also a sweep generator + HP8568 SA.
--- Zach N0ZGO
I've considered getting Mini-Circuits high and low pass filters to go between my handhelds and my Arrow antenna. But the datasheets for the ones that I looked at only rate the filters at 0.5W. I'd be pushing about 5 W through them. Does anyone here have experience doing that to these filters and can comment on whether that works or not? Are there Mini-circuits filters that will handle 5 W comfortably? Steve AI9IN ----- Original Message ----- From: Jerry via AMSAT-BB (amsat-bb@amsat.org) Date: 05/24/20 14:45 To: Andy Brian (briaandy@gmail.com) Cc: amsat-bb (amsat-bb@amsat.org) Subject: Re: [amsat-bb] RS-44 VU noise from TX
Hoi,
Instead of putting a diplexer as filter( best is to use 1 per band), if you have the possibilty to make stuff your own, just 'split' a diplexer by making an LPF (low pass filter) at the 2m antenne and a HPF ( high pass filter) at the 70cm antenne. Or find some to buy (MINI CIRCUITS maybe?). This way you have a filter at both antennas. Mostly a diplexer is used only on one antenna, while the other diplexer port is closed with a small dummy load. Keep in mind the tx-pwr!
Best 73's
Jerry,ON4CJQ
participants (5)
-
Andy Brian -
Mark L. Hammond -
on4cjq＠telenet.be -
Steve Kristoff -
Zach Metzinger