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VHF Quantar Duplexer 600KHz?

Posted: Wed Nov 29, 2017 4:21 pm
by escomm
Manual says something like 200KHz of bandwidth at 1.5MHz separation and 600KHz of bandwidth at 2.5MHz separation. Has anyone used them on a 600KHz split and how was the insertion loss and other performance?

Re: VHF Quantar Duplexer 600KHz?

Posted: Fri Dec 01, 2017 9:13 am
by chartofmaryland
Afternoon Escomm,

When you are speaking of the bandwidth, are you asking about the bandpass bandwidth of the high and low side of the duplexer?

The minimum seperation between transmit and receive frequencies will always stay at 1.5 Mhz Tx to Rx or 2.5 Mhz Tx to Rx.

The flat pack duplexer from Fingu is lacking the Q to perform at 600 Khz Tx to Rx frequency spacing.

We have tuned a few to try and the best we could run with around 2 dbm desense was 3 watts on transmit while still getting -119 dbm on receive.


Re: VHF Quantar Duplexer 600KHz?

Posted: Sat Dec 02, 2017 8:18 am
by escomm
Sorry I was talking about the rack mount one. I think the current part number is 9175300H02

Re: VHF Quantar Duplexer 600kHz?

Posted: Sat Dec 02, 2017 9:54 am
by Astro Spectra
Hi escomm, that set of cans has a minimum t to r split of about 1.2 MHz. It's a bandpass-bandpass design. At the narrowest spacing the pass band is about 100 kHz aside , meaning the width of the high and low pass bands.

It's not big enough really for the ham split, you need something with 'more can' i.e. larger cavities. My favourite is the Sinclair Q2220. My other favourite is Nobu at Ceasers :)

Re: VHF Quantar Duplexer 600KHz?

Posted: Mon Dec 04, 2017 11:58 am
by escomm
Holy crap, that thing is not BP/BR???

Re: VHF Quantar Duplexer 600KHz?

Posted: Mon Dec 04, 2017 12:16 pm
by Astro Spectra
There is a notch set by the a small tuning cap but from memory it's shallow at only 30 to 40 dB at the narrow splits, deeper at the wide splits. Because the main elements are electrically shortened the notch performance is not great.

Re: VHF Quantar Duplexer 600KHz?

Posted: Tue Jan 30, 2018 3:34 pm
by Karl NVW
I believe the numbers Escomm is looking at are for the preselector filters. TxRx has a very nice six 10" can BPBR design that is specifically built for 600 KHz T-R separation. Bandwidth of each leg (for alternate operation on two channels) is about 67 kHz with slightly degraded performance: additional 0.8 dB insertion loss and 9 dB less isolation. NOTE: That's for 2 channels, NOT two separate repeater stations simultaneously!!

Re: VHF Quantar Duplexer 600KHz?

Posted: Thu Feb 08, 2018 11:14 am
Without pulling out the spec sheet on those, my memory says they really were for 2mhz or more.
They are best suited as a filter for a frequency agile base station, hence the 200 khz of bandwidth and the reason for BP rather than BR.
You can use these for "protection" of a remote base at a repeater site and get great sensitivity even near other transmitters. Assuming of course that they TX of the other transmitter and the RX of the base are appropriate. Same with the opposite (RX to the station TX).
I have messed with these extensively and closest "spacing" that I found usable was around 1 mhz.
We are using them around 1.2 mhz with 9/10's dB loss on one side, and 1.5 dB loss on the other. They are not wanting to be reciprocal on the loss when tuned that close. You kinda get what you get.
The loss goes WAY up as you get below 1.2 mhz or so.
Our use is a bi-directional "simplex to simplex" repeater.