Something weird - mooraker 100 pre-amp

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Something weird - mooraker 100 pre-amp

Postby mickydt » Fri Mar 08, 2019 8:19 pm

today i was mucking around with different aerials and also a pre-amp in line while carrying out a search with the uniden sds100 it landed on a known nxdn signal but yet no audio decode, i knew well that the frequency was in use.

i mucked around with various radio settings but still no decode so then decided to take the pre-amp off and then behold the uniden was decoding nxdn audio which has got me perplexed.

any ideas as to why this would happen? the pre-amp is the mooraker 100 i have had it for ages and back then it didn't cost me what they are asking for now.
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Re: Something weird

Postby jimh » Fri Mar 08, 2019 11:28 pm

How strong is the signal you receive without the pre-amp?

I'd guess the pre-amp is either overloading the front end of your scanner (...and it's already a strong signal to start with) or perhaps your pre-amp isn't working at all and you're receiving no signal out of it?
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Re: Something weird - mooraker 100 pre-amp

Postby m0lsx » Sat Mar 09, 2019 1:13 pm

It is worth remembering that a pre amp amplifiers does little more than simply amplifies the volume of everything, rather than just the desired signal. So it could be that you have a strong local signal on a different frequency that is overloading the radio & the radio is thus not behaving as it should. It could also be down to the higher noise level on the signal after everything has been amplified.
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Re: Something weird - mooraker 100 pre-amp

Postby mickydt » Sat Mar 09, 2019 9:33 pm

it is possible that the pre-amp been so old is on its way out but at the same time it was fine when picking up dmr signals in scan mode, in scan mode though i noticed i wasn't getting any nxdn. with the pre-amp on there was considerable signal difference.

without the pre-amp in line the nxdn was back and decoding!

couldn't really test it today best time around here is during the week.

basically i have 3 aerials and no not all running together :smiles:

i will give the experiment another bash sometime next week
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Re: Something weird - mooraker 100 pre-amp

Postby mickydt » Wed Mar 13, 2019 3:12 pm

i did manage to get the decoding working (nxdn) with the amp but it also suggests that with the pre-amp been so old that it may be on its way out as in my posts i mentioned that i couldn't get a decode when i first tried.

i have my eye on another not moonraker though just like to experiment with things as just listening can get a bit boring.

also just got a sdrplay not opened it yet but will give me something to do later on in the months to come.
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Re: Something weird - mooraker 100 pre-amp

Postby m0lsx » Wed Mar 13, 2019 4:16 pm

These cheap & poorly designed wideband Pre-amps often do, cause all sorts of problems.
First, they go the wrong end of the coax, so where the wanted signal is at it weakest.
Second, they are wideband & thus amplify everything across their whole spectrum, not just on a desired band.
Third & as a direct result of problem two. They have no form of filtering to stop any unwanted overload problems from local strong signals.
Fourth. There is a very good reason why they cost a fraction of the cost of a single band pre-amp. They are cheap & nasty designs.
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