Low Noise Amp

[dave3825]

Has anyone ever tried one of these or something similar and have and comments?

Low Noise Amplifier 100 kHz to 2000 MHz RF LNA Gain 30dB Operates to 5 GHz USB | eBay

Thanks

 

[jwt873]

I haven't tried that amp (or any like it) that you posted the link to. But there sure was some interesting stuff on that page

Do you need an amp going to 5Ghz? Not much voice going on there.

Also, 30 dB seems like a lot, you may have to pad it or have a way to reduce the gain or switch it in and out of the antenna circuit in order it to prevent it from overloading local signals.

Thanks for posting the link, I just bought this one... Only good to 2 GHZ I plan to put it in a metal case with an antenna relay and use it as a mast mounted pre-amp for my 432 Mhz SSB/CW Yagi.

1 2000MHz 30dB 2GHz Low Noise LNA RF Broadband Amplifier Module HF VHF UHF | eBay

 

[dave3825]

I was just using the 5 ghz one as an example. I would like to try one and would also put it in a case. What I did like about the one I posted is that it is powered by USB which makes it nice if your out with a laptop, then the power would not be an issue. But if I was in the car, I'm sure it would run off the cigarette lighter. And with a case, I am sure it could be outfitted with a connector to utilize either a 12 volt dc plug or a 12 volt walwart. In any event please post your results when you get yours..

 

[cmdrwill]

Has anyone ever tried one of these or something similar and have and comments?

Low Noise Amplifier 100 kHz to 2000 MHz RF LNA Gain 30dB Operates to 5 GHz USB | eBay

Thanks

I have one of those on the way. My use will be to amplify a service monitor signal generator to tune duplexers. I will post back my resaults.

 

[prcguy]

That amp has too much gain and too small of an IP1 for use as an antenna preamp. It will compress at 12dBm and with 30dB gain the average RF level picked up in your neighborhood will probably create lots of Intermod unless you have a band specific filter in front of it.

Generally a preamp for a receiver like a repeater or a VHF/UHF SSB rig will have less than 20dB gain and 15dB is a good goal. If you are not going to use a band pass filter in front of it then look for a preamp with both low noise and an IP1 close to or above 30dBm. When you see the cost of a preamp like this you'll know why very few people have them.
prcguy

I haven't tried that amp (or any like it) that you posted the link to. But there sure was some interesting stuff on that page

Do you need an amp going to 5Ghz? Not much voice going on there.

Also, 30 dB seems like a lot, you may have to pad it or have a way to reduce the gain or switch it in and out of the antenna circuit in order it to prevent it from overloading local signals.

Thanks for posting the link, I just bought this one... Only good to 2 GHZ I plan to put it in a metal case with an antenna relay and use it as a mast mounted pre-amp for my 432 Mhz SSB/CW Yagi.

1 2000MHz 30dB 2GHz Low Noise LNA RF Broadband Amplifier Module HF VHF UHF | eBay

 

[dave3825]

@ prcguy

Which one are you speaking of? The one I posted or the one jwt873 bought? I know top quality is expensive and unfortunately I am on a strict budget.

Thanks

 

[mancow]

I recently bought one of these but haven't tested it yet. Unless I'm mistaken the specs look good. I'll report back with how it does.

1PC High linearity LNA module/50M-4G 0.6dB noise figure/RF low noise amplifier

 

[M105]

I use one of these super expensive amplifiers on both my outside TV antenna and SDR setup. They work great when placed right at the antenna and don't cause any overloading. That said, I don't listen to anything over 1GHz. If I did, I would switch to a satellite amp. My 2 cents worth, don't overthink it as it is still just FM radio.
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Emerson 10dB Digital TV Signal Booster Amplifier Amp for Indoor Outdoor Antennas | eBay

 

[dave3825]

I mainly listen to sdr in the tband. But also use Unitrunker to listen to a 700 and an 800 mhz trunked system. There's a 500mhz that I switch to here and there cause I can only listen to 2 trunked systems with 2 dongles. Getting an airspy will increase that. I am getting most likely the airspy and spyverter combo soon. I would like to try to listen to the cothen stuff as I am not far from the shores of Long Island.

 

[dave3825]

Thanks for posting the link, I just bought this one... Only good to 2 GHZ I plan to put it in a metal case with an antenna relay and use it as a mast mounted pre-amp for my 432 Mhz SSB/CW Yagi.

1 2000MHz 30dB 2GHz Low Noise LNA RF Broadband Amplifier Module HF VHF UHF | eBay

I have one of those on the way. My use will be to amplify a service monitor signal generator to tune duplexers. I will post back my resaults.

I recently bought one of these but haven't tested it yet. Unless I'm mistaken the specs look good. I'll report back with how it does.

1PC High linearity LNA module/50M-4G 0.6dB noise figure/RF low noise amplifier

Have any of you guys tested these out and if so, good, bad or undecided?

 

[dave3825]

I just ran across this now. I really dont know much about the specs as to if they are good or not. .

LNA for all




.

 

[dave3825]

Has anybody got and used the amps they mentioned?

 

[jwt873]

I've got the one I ordered from eBay. It arrived a couple of weeks ago, but I haven't done anything with it yet. 1 2000MHz 30nu ll2G HzL OWNoi seL NA RFBroadba ndAmplifi erModu le HFV HFU | eBay

All I have to do now is get around to hooking it up and see whether or not it swamps the front end or not. Apparently you can reduce the gain significantly by lowering the voltage. If it works, I'll probably wind up putting it in a small metal case.

I should have time this weekend to break out the soldering equipment and get going on it.. I'll report back.

 

[RFI-EMI-GUY]

I've got the one I ordered from eBay. It arrived a couple of weeks ago, but I haven't done anything with it yet. 1 2000MHz 30nu ll2G HzL OWNoi seL NA RFBroadba ndAmplifi erModu le HFV HFU | eBay

All I have to do now is get around to hooking it up and see whether or not it swamps the front end or not. Apparently you can reduce the gain significantly by lowering the voltage. If it works, I'll probably wind up putting it in a small metal case.

I should have time this weekend to break out the soldering equipment and get going on it.. I'll report back.

If you lower the supply voltage you will rduce the intercept point and thus more susceptible to intermodulation.

Rules of thumb for a low noise preamp (LNA)

An LNA is most useful when mounted at the antenna (Mast head preamp).

Wide band is bad, you will get overload from out of band signals like TV and FM. Use a bandpass filter before the LNA tuned to the band of importance. This means, for most DC-Daylight SDR operations, you will have to compromise one way or another.

Too much gain causes receiver performance to suffer. Install an attenuator BETWEEN the LNA and the receiver. The attenuation should be enough to cancel most of the LNA gain less the feedline loss, An easy way to optimize the system is with a variable attenuator and a weak signal, preferably radiated from a nearby signal generator. Adjust the attenuation until the signal weakens and then reduce attenuation about 3 dB. I use the SINAD method to do this, using a 12 dB SINAD reference, I increase attenuation until the 12 dB SINAD degrades (to 8-10 dB SINAD), then increase back to 12 dB SINAD, note attenuation and then reduce attenuation 2 or 3 dB making signal just slightly hotter.

 

[jwt873]

UPDATE

I had some time so I dug out the soldering iron, my variable power supply and some SMA to 'N' adapter cables. Once I had the power leads soldered, I connected the amp to my TS-2000 near the radio's input. (I plan to go mast mounted some day). I used an SMA barrel adapter to join the two cables to provide a direct connection without the amp.

There were no operating voltages specified for the amp, so I tried from 3V to 12V. It seems that 6 Volts provided the best balance between noise and a louder signal.

I'm interested in UHF weak signal work, so I first tuned in a CW beacon on 432.301 Mhz that is 60 miles away. It was down in the mud, but I could copy it. When I put the amp in line it increased the noise quite a bit, but the signal came up as well. It was definitely easier to copy. I'm going to try it again when I meet some friends on 432.100 Mhz SSB next Tuesday.

But, I'm sure most here are interested in FM

I was using my 11 Element horizontally polarized UHF Yagi. I turned it so it was broadside to a local repeater that's 30 miles away. With the amp out, the repeater gave me an S meter reading of 5. With the amp in-line it pinned the meter. The audible noise on the signal was negligible.

So, it seems to do something See images below.

 

[jwt873]

Wide band is bad, you will get overload from out of band signals like TV and FM. Use a bandpass filter before the LNA tuned to the band of importance. This means, for most DC-Daylight SDR operations, you will have to compromise one way or another.

Yes, I'm only interested in 432 Mhz, but for listening across a broad range of frequencies, it could pose a problem with intermods etc. If it works out, I plan to go mast mounted with a transmit/receive relay.

I don't know if it does add that much for FM.. Just thinking about it... The S5 signal was just as clear as the +60dB signal, so did I gain anything? I'll have to try some further testing on weaker FM stations.

 

[jwt873]

One more demo to show how it performs... I took a video of the meter while copying the VE4ARM beacon with and without the amp.

The first 16 seconds is with the antenna by itself. Then I cut in another 16 seconds with the amp inline...

The Kenwood TS-2000 has never been known as the most sensitive rig on the market. But in any case, the amp does work and makes a noticeable difference on UHF CW.

https://www.youtube.com/watch?v=UGtarwN1L2s&feature=youtu.be

 

[cmdrwill]

The Low Noise Amplifier 100 kHz to 2000 MHz RF LNA Gain 30dB Operates to 5 GHz from eBay works very well on my service monitor to boost the signal generator out put for testing and tuning cavities and duplexers. I am going to add another amp to boost the output above + 10 DbM.

 

[RFI-EMI-GUY]

Yes, I'm only interested in 432 Mhz, but for listening across a broad range of frequencies, it could pose a problem with intermods etc. If it works out, I plan to go mast mounted with a transmit/receive relay.

I don't know if it does add that much for FM.. Just thinking about it... The S5 signal was just as clear as the +60dB signal, so did I gain anything? I'll have to try some further testing on weaker FM stations.

With FM, once you approach full quieting you won't notice the gain. However, having a lower noise figure than the receiver, yes it will improve the weak signals.

Bear in mind when you install one of these 'naked" low noise preamps on a receiver, it will indeed provide apparent improvement over the "filtered" high Intercept point preamp inside the receiver. This is at the risk of the possibility of overload and IM.

I had a Syntor mobile in my company car in Chicago. It had the "factory preamp" option. When out in Iowa, Wisconsin and western Illinois, repeaters could be heard and accessed for 70 to 100 or more miles. When in downtown Chicago the Inter-Mod was apparent.