Batboard

I'd like to take a VHF 100W quantar, who's life has been spent as a T1R1 repeater, and convert it to a T8R8 base station.

The only issue I anticipate is the reciever preselector bandwidth. The freq's the base will need to be capable of will be +/- 2.5 MHz. Should I expect any serious RX degredation? Is there a VHF reciever module that is wideband, and does not require tuning? I'm willing to accept some reduction in selectivity.

I expect the PA will be able to handle the variation in TX frequencies, but we'll see...

I am thinking I will retune for a midpoint frequency and see how the reciever fairs on the required frequencies. Anyone done this? Any tips?

Jason wrote:I'd like to take a VHF 100W quantar, who's life has been spent as a T1R1 repeater, and convert it to a T8R8 base station.

The only issue I anticipate is the reciever preselector bandwidth. The freq's the base will need to be capable of will be +/- 2.5 MHz. Should I expect any serious RX degredation? Is there a VHF reciever module that is wideband, and does not require tuning? I'm willing to accept some reduction in selectivity.

I expect the PA will be able to handle the variation in TX frequencies, but we'll see...

I am thinking I will retune for a midpoint frequency and see how the reciever fairs on the required frequencies. Anyone done this? Any tips?

You will get a 4 meg bandwidth from the tuned preselector.

Jim

Agreed, and I speak from experience. 4MHz bandwidth on those preselectors.

You'll be fine.

I am thinking I will retune for a midpoint frequency and see how the reciever fairs on the required frequencies. Anyone done this? Any tips?Jason

If you are thinking of doing this, you might never achieve the sensitivity you expect in the receiver.

Sweep tuning is pretty much the defacto standard for tuning preselectors properly, otherwise you get notches in the wrong places and degraded peformance across your bandwidth.

If you are tuning for a single channel pair, and the operation is wideband, then tune under narrowband conditions to fine tune the preselector to work better as you tuned for a narrower spread, so it should be easier to get the best S/N ratio and still maintain proper selectivity and sensitivity.

But for multi-channel, wireline operation, sweep tuning is the only way.

n7maq wrote:You will get a 4 meg bandwidth from the tuned preselector.
Jim

Can anyone confirm this is also true on a UHF R2? I've swept the front end using a IFR1600 w/ tracking gen and it's nearly 5MHz wide at the -3dB points. I'm getting about 2dB I.L. Is that typical as well?

I'm used to the MSF5000 which had a tight enough front end for in-cabinet repeat but the wide frequency response of the Quantar took me by surprise. Guess having only 3 little helicals shouldn't surprise me.

Has it been anyone's experience that this is good enough for a split antenna installation on a hilltop? Without a BpBr duplexer inline, I'm worried the Rx is going to get hammered. It'll be on a master Rx system but the window filter is 4MHz wide anyway to cover all the other repeater inputs.

Thanks in advance for any insight/experience.