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WIRES Node getting into my packet station

Feb 1st, 21:42

N1AUP

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
I have a 2 meter FM packet station handing NTS traffic. It sits on 145.09. That radio runs 80 watts to an outside antenna at 30 feet.

I also have a WiresX node running at 147.48 FM. The outside antenna sits at 50 feet. Each is about 25 feet from the other.

Both antennas are fed with LMR400.

The 5 watt Wires node blows away the packet station, making it deaf to the outside packet world. And visa versa. The 80 watt packet station interferes with the WIRES node. The interference disappears when I disconnect the antenna from the radio (meaning it's not coming in on the power connnection.

Is there a filter that I can build that can notch out the 147.48 signal, so the WIRES station does not trash the packet station? And the 145.09 packet signal.

Thanks
Christine
N1AUP
Feb 2nd, 05:16

W1VT

Super Moderator

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
JUN 1972 - QST (PG. 48)
http://p1k.arrl.org/pubs_archive/62137
Taking Out the 2-Meter Garbage
Author: Moler, Donald, WA1MRF
Keywords: CONSTRUCTION HOMEBREW VHF 2 METER FILTER GARBAGE CAN
A high Q filter constructed out of a 32 gallon galvanized trash can.

https://www.homedepot.com/p/Behrens-31-Gal-Galvanized-Steel-Round-Trash-Can-with-Lid-1270/100202118
https://www.lowes.com/pd/Behrens-31-Gallon-Silver-Galvanized-Metal-Trash-Can-with-Lid/3475295
Slightly less Q than 32 gallons but close enough as the filter is tunable over wide range.

Zak Lau W1VT
ARRL Senior Lab Engineer
Feb 9th, 03:56

N1AUP

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
If I am understanding things correctly, this will allow you to pass RF at a certain frequency, and reject everything else. This would be useful on either the packet station or the Fusion node to filter out everything except what this system wants to see.

Is it possible to build something that does the exact opposite? Meaning something I could attach to the radio that connects me with repeaters and simplex stations to notch out the packet signal, and the fusion signal? In this case, I don't want to solely allow one frequency through. I want to notch out one frequency.

And curious if you could do this digitally? Meaning software reads the frequency of the incoming signal, and if it matches the packet traffic or fusion traffic, it blocks it, while retransmitting what doesn't match?

Feb 9th, 08:39

W1VT

Super Moderator

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Yes, if you connect a resonant cavity across a coaxial transmission line it will act as a notch filter. An open quarter wave stub made out of coax will do the same, but you need a very low loss cavity or stub if you want a very narrow notch.

You could implement a PIN diode switch to gate the signal. I don't know whether this is be useful for your application, but yes, you can connect a frequency counter to a fast electronic switch. This technique of using a frequency counter for control is used in automatic antenna tuners and modern solid state amplifiers.

Zak W1VT
ARRL Senior Lab Engineer
Feb 10th, 05:58

N1AUP

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Do you have an article reference for the frequency counter / gate switch idea?

Thanks
Feb 11th, 05:57

W1VT

Super Moderator

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
https://swharden.com/blog/2016-10-10-raspberry-pi-rf-frequency-counter/
"Previously I've built standalone frequency counters, frequency counters with a PC interface, and even hacked a classic frequency counter to add USB interface (twice, actually). My latest device uses only 2 microchips to provide a Raspberry Pi with RF frequency measurement capabilities. The RF signal clocks a 32-bit counter SN74LV8154 ($1.04 on Mouser) connected to a 16-bit IO expander MCP23017 ($1.26 on Mouser) accessable to the Raspberry Pi (via I²C) to provide real-time frequency measurements from a python script for $2.30 in components! Well, plus the cost of the Raspberry Pi. All files for this project are on my GitHub page."

Zak W1VT
ARRL Senior Lab Engineer
Feb 20th, 16:24

N1AUP

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Thanks. Thinking....


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