Preamp and filter recommendation

[ih784]

Good morning,

I am listening to VHF frequencies 156.000–162.050 MHz and am looking into getting a preamp and filter for either my airspy mini or my RTL-sdr(s) (they use separate antennas). Is there any combination that seems to work well or a general consensus?

 

[ka3jjz]

Before you go this route what are you using for an antenna and coax? The general consensus on this is to improve these first

Mike

 

[ka3jjz]

Also how high up is the antenna? It should be high enough to clear any obstacles like trees....Mike

 

[ih784]

I’ve got an Omni-X antenna and 800-900mhz specific antennas. The coax is RG6 quadshield and a 35’ run. I know the coax could/should be better but, it works. The antenna is 25’ in the air.

 

[wgbecks]

I am listening to VHF frequencies 156.000–162.050 MHz and am looking into getting a preamp and filter for either my airspy mini or my RTL-sdr(s) (they use separate antennas). Is there any combination that seems to work well or a general consensus?

A good low noise preamp can be helpful. But you need to consider the local noise floor that can be quite high on VHF with all of the
electronic pollution we have anymore. Another factor to consider is the performance specifications of a given preamp in handling
strong signals such that it doesn't contribute intermodulation (IP3) products in addition to the need to have a low noise temperature.

 

[hazrat8990]

I'm running the amplifier from Airspy and I'm quite pleased with it. The sites closest to me are VHF, and I have antennas that work pretty well. However, there is an 800MHz site that is almost to 30 miles away that doesn't even show the slightest blip on the waterfall. I ended up buying a surplus LSM 800MHz antenna from eBay and hooked the amp to it. The site now comes in around -82dbm according to my SDS200 scanner, and that signal is split with an RTL-SDR V4. I am now able to monitor the site on my scanner, as well as SDR Trunk. The VHF sites are strong enough for me to need to turn on attenuation, and the band mismatch with the 800MHz antenna make the noise floor super low.

 

[Ubbe]

If you can get a VHF bandpass filter then that would help a lot. Then a preamplifier could also be used without overloading you SDR receivers. You will still need to reduce the signal from a preamp to give maybe 6dB gain at most. Having the preamp at the antenna would give more benefits like impedance matching and not loosing any signal to coax attenuation.

It will depend of how many strong radiosignal there are at your location, if you will need a filter before the preamplifier or can have it down at the receiver and can then disconnect it and listen to other frequency bands.

A 35' length of RG6 coax at VHF doesn't hardly attenuate anything so you can start by evaluating filter and amplifier at the receiver.

BPF-VHF Band Pass Filter | Scanner Master

BPF-VHF Band Pass Filter

www.scannermaster.com

This preamplifier are only for VHF, so must have some filter as well but I do not know how it performs.

LNA-VHF-B Pre-Amplifier | Scanner Master

LNA-VHF-B Pre-Amplifier

www.scannermaster.com

ATT-20 Variable Attenuator | Scanner Master

ATT-20 Variable Attenuator

www.scannermaster.com

/Ubbe

 

[ih784]

BPF-VHF Band Pass Filter | Scanner Master

BPF-VHF Band Pass Filter

www.scannermaster.com

This seems to fit the bill to a T. I'll see if I can find one in stock somewhere. Thank you Ubbe!

 

[prcguy]

Here is exactly what you need, a brick wall filter that passes only 156 to 162MHz then cuts off sharply above and below. With this filter you can use a fairly inexpensive preamp and the filter will protect it and the receiver very well from out of band interference. I got this DCI filter off eBay in the $60 range, although its pretty expensive new.

 

[vagrant]

I enjoy those DCI filters as well. Still, for a lower cost alternative, perhaps a PAR filter will suffice. Contact Dale with your needs.

PAR Electronics | Filters for the commercial 2 way market, MATV, FM broadcast, laboratory, marine industry, amateur radio, scanner and short wave listening enthusiasts

PAR Electronics Inc. Filters for the commercial 2 way market, MATV, FM broadcast, laboratory, marine industry, amateur radio, scanner and short wave

www.parelectronics.com

 

[ih784]

Here is exactly what you need, a brick wall filter that passes only 156 to 162MHz then cuts off sharply above and below. With this filter you can use a fairly inexpensive preamp and the filter will protect it and the receiver very well from out of band interference. I got this DCI filter off eBay in the $60 range, although its pretty expensive new.

View attachment 169729

I have found a lot of good (used) equipment on eBay. Ill start hunting for one of these as well in my particular frequency range.

 

[ih784]

I enjoy those DCI filters as well. Still, for a lower cost alternative, perhaps a PAR filter will suffice. Contact Dale with your needs.

PAR Electronics | Filters for the commercial 2 way market, MATV, FM broadcast, laboratory, marine industry, amateur radio, scanner and short wave listening enthusiasts

PAR Electronics Inc. Filters for the commercial 2 way market, MATV, FM broadcast, laboratory, marine industry, amateur radio, scanner and short wave

www.parelectronics.com

I sent him a message, are these folks pretty reasonable to deal with?

 

[vagrant]

Dale is no problem. I have over 10 of his various filters. He does get busy with commercial orders, so if he does not reply after a few days, email him again. Tell him what you are doing and what your needs are.

 

[ih784]

Will do. It seems bandstop filters in this range are few and far between.

 

[dlwtrunked]

I'm running the amplifier from Airspy ...

I assume you mean the Uputronics [er-amp sold by Airspy.US--not really an Airspy product (not on their own, Airspy.com website. A preamp at the antenna would be better but there is not a good selection of those (I put good pre-amps in a salvaged TV mast mount pre-amp box after taking the original out)> Regarding "consensus", there can be none as individual situations vary--not only what you are trying to hear (once direction or omni-directional etc), whether you have nearby strong stations including their frequency and how close, nearby hills, etc. In my experienceexperimenting yield the best results but certainly not the least cost or effort.