[VHFcontesting] 6M and 2M Bandpass Filters

[Lloyd - N9LB]

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 at contesting.com] On Behalf Of John O’Mara
Sent: Friday, April 08, 2022 11:53 AM
To: VHFcontesting at 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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