Many of my VHF and UHF Yagis share a common mast.
I had to add quarter-wave stubs to the inputs of my 50 MHz, 144 MHz, 222 MHz
and 432 MHz transverters to prevent the burn-out of the front-end PHEMPT
MOSFETs when transmitting on other VHF bands.
The quarter-wave stubs are fairly broadband, not suitable for notching in-band
or band-edge interference.
I also gained about 10 dB reduction in FM and VHF TV broadcast RF getting into
the front end devices. Seemed like that improved the received noise-floor.
73
Lloyd - N9LB
-----Original Message-----
From: VHFcontesting
[mailto:vhfcontesting-bounces+lloydberg=tds.net@contesting.com] On Behalf Of
John O’Mara
Sent: Friday, April 08, 2022 11:53 AM
To: VHFcontesting@contesting.com
Subject: [VHFcontesting] 6M and 2M Bandpass Filters
Good morning,
I’m part of the W4IY Flagpole Knob VHF Contest Group (FM08jm). We have been
operating from Flagpole Knob continuously for over 30 years. Thanks for all the
Qs.
We experienced higher than normal interference between our 6 and 2M stations
during September last year and I wanted to look into what others may be using
and their experiences with bandpass filters, stubs, etc. to minimize
interference between stations. We are running 500W on 6M and 1.2KW on 2M. We
try to space the antennas as far apart as possible but the the top of the Knob
is only so big.
I appreciate any assistance you can provide. Thanks and 73, JackW4NF
W4IY 4300’ ASL FM08jm
Sent from my iPad
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