I'm Looking for installation/use information for the Stridsberg PRE-20 Receiver Pre Amplifier.
Any input (no pun intended) will be greatly appreciated!
Any input (no pun intended) will be greatly appreciated!
Stridsberg PRE-20 Receiver Pre Amplifier
- Thread starter PD47JD
- Start date
rf_patriot200
Active Member
There's actually one of these for sale in the RR Classifieds section for $120 , unless it's gone.
The Stridsberg PRE-20 is pretty lousy by todays standards, are you sure you want to put it in line?
'Tis no more!
Always experimenting....but there must be somewhere floating around an explanation on its use. To wit: There is an antenna input, o.k.; there is an antenna to receiver output, o.k. and there is a 12volt input., o.k. But, on the antenna output side of the case, there is a red arrow that points to "DC injection port +16 volts max" printed in red. Is that referring to a Bias-Tee? (Which has its own 12 volt input). So, what is the purpose of the 12 volt input on the PRE-20?
On to another issue (question) in light of your well-received observation that the "PRE-20 is pretty lousy by today's standards", what would you recommend? (Yes, I have a copy of the latest DX Engineering Catalog in hand).
Looks like it has a built in bias Tee for using power fed up the coax into the output port and you can get an optional 12v input on the case via a bypass cap. If you up the P1 specs by at least 10dB into the 22dBm to even 27dBm range which will up the IP3 specs to the 35dBm to 40dBm range it will survive in many more places without overloading and creating IMD. A lower noise figure would be nice like under 2dB for a high power handling preamp with the specs I tossed out. With the wimpy IP1 and IP3 specs of the PRE-20 I would expect the noise figure to be at .5dB or less but instead it’s 3.5dB.
If you can live with slightly elevated noise figure I usually recommend a Minicircuits ZHL-1010 with a flat 10dB gain from 50MHz to 1GHz, IP1 of 26dBm, IP3 46dBm and a noise figure around 3.5dB. New price is $149 but they show up on eBay in the $50 range. The PRE-20 is $179 and can’t come close to the ZHL-1010 specs. There is a similar Minicircuits ZHL-2010 with 20dB gain but the additional gain can also push it into IMD land if your in RF he’ll like me. I think a 1010 is fine for feeding one to four receivers and a 2010 maybe eight to twenty four receivers with some attenuation to keep overall gain around 2dB to each receiver.
It’s hard to find or very expensive to find a high level preamp like the ZHL-1010 with lower noise figure but they are probably out there. There are mid level range preamps with IP1 around 22dBm or 10dB higher than the PRE-20 and low noise figure of .5dB but most have a gain slope problem where they can have 24dB gain at 50MHz but 15dB gain at 1GHz which is not ideal. One example is the Minicircuits ZX60-P103LN.
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Received and digesting at 11:21pm EST.
Ubbe
Member
A scanner usually overloads more easily at lower frequencies so a flat gain or inverted slope are preferred. If inserting a 4,7pF capacitor in line with the signal after the amplifier it would attenuate 2dB at 900MHz and 10dB more at 50MHz that would make it give a 15dB gain over the whole frequency range.
If monitoring 25MHz it would give only a 6dB gain and in that case a 1000 Ohm resistor in parallel with the capacitor will never let it go below 15dB gain.
If using a coax that attenuates a lot at 900MHz you can use a smaller capacitor like 2,7pF that would give a 3dB attenuation at 900MHz and 20dB at 50MHz, without a bridging resistor, that will compensate both for the slope of the amplifier and the coax loss at higher frequencies.
/Ubbe
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