Diplexer Choices

[James04TJ]

I am replacing a scanner antenna setup at a government facility. There is a need for reception of VHF-LO, VHF-HI, UHF, and 700/800 Public Safety bands over a very large area. I currently have a commercial VHF-LO antenna in place at about 30' AGL that can handle the low band and am considering a DPD 118-1000 LP (to be mounted 60' AGL) to provide coverage on the remainder. To make this work I need to locate a diplexer to split the VHF-LO from everything else into the feedline (150' of LMR-600). Is anyone aware of a diplexer that fits the bill?

 

[kb2vxa]

You'll have to do your homework, every installation is different. The point is you must consider the frequency bands and choose the low, high and crossover frequencies accordingly.

 

[prcguy]

I have a Comet CF-530 that's rated for 1.3-90MHz on one port and 123 to 470MHz on the other but it probably works fine past 800MHz. I can sweep it this weekend and let you know. You might benefit from a good preamp at the hi freq antenna if your not in a heavy RF area.
prcguy

 

[James04TJ]

I have a Comet CF-530 that's rated for 1.3-90MHz on one port and 123 to 470MHz on the other but it probably works fine past 800MHz. I can sweep it this weekend and let you know. You might benefit from a good preamp at the hi freq antenna if your not in a heavy RF area.
prcguy

A pre-amp is out of the question... This will be installed in a very heavy RF area that includes multiple transmitters (located within 50') on HF, VHF-Low, VHF-High, 700MHz, and 800MHz.

I would be very interested in the attenuation of 800 on the Comet though. 800 is more important to me than low band so if there is much attenuation I would rather skip the diplexer in favor of just accepting the losses of the DPD on low band.

 

[lmrtek]

...............

 

[trooperdude]

I am replacing a scanner antenna setup at a government facility. There is a need for reception of VHF-LO, VHF-HI, UHF, and 700/800 Public Safety bands over a very large area. I currently have a commercial VHF-LO antenna in place at about 30' AGL that can handle the low band and am considering a DPD 118-1000 LP (to be mounted 60' AGL) to provide coverage on the remainder. To make this work I need to locate a diplexer to split the VHF-LO from everything else into the feedline (150' of LMR-600). Is anyone aware of a diplexer that fits the bill?

Plug this:
Diamond® Antenna ~ MX3000 Triplexer
into the 300-950 port on this:

Diamond® Antenna ~ MX2000 Triplexer

.15-.40dB of insertion loss which ain't bad.

And then you can add narrower band-specific antennas for your needs.

Cheaper than TinLee's current prices for custom diplexers too.

 

[prcguy]

I swept the Comet CF-530 and it had some ripple above 500MHz that reached about 1.5dB loss on peaks, otherwise the average loss was around .8dB up to 1GHz. It would certainly work if the ripple doesn't bother you. I also tried a Comet CF-360 rated for 1.3 to 30MHz on one port and 49 to 470MHz on the other port and it was much cleaner between 500Mhz and 1GHz with about .8dB loss at 850MHz.
prcguy

 

[James04TJ]

Thanks prcguy... I think that I am going to wait to see how the DPD does on low band and if needed add the diplexer and low band antenna. I would rather have loss on low band due to antenna resonance than on 800 due to system loss.