Use 6 dB pads on the TG output and SA inputs for the most accurate filter? alignment. The possible detuned duplexer notches will be on the RX cans that are tuned to reject the TX frequency.?
?
John
---------- Original Message ----------
From: "John via groups.io" <jhaserick84@...>
Date: 03/15/2025 9:01 AM EDT
Subject: Re: [repeater-builder] Quantar TFD6512A Preselector Filter
?
?
Hi Jeff,
?
Once you get the flat top response curve with minimum loss, you ideally should check at your operating frequency, with a return loss bridge connected to the filter input with the receive end of the filter connected to a 50 ohm load, (to keep from detuning the duplexer notch,) then again with the receiver or RX pre-amp connected. Keep the level of the tracking generator to below -10 or -20 dBM so as not to overload the RX or pre-amp.?
?
If you do not have a RLB, you could use an antenna bridge on your RX frequency, with the 50 ohm load, but not the RX input, as the antenna bridge output is most likely at too high a level for anything solid state to handle without detuning..
?
John
On 03/14/2025 8:26 PM EDT Jeff Acree via groups.io <locustpointlight@...> wrote:
?
?
Friends,
?
I need to retune the subject preselector and was wondering if there are any procedures someone could share or point me to.? I have a HP8320B and a HP8935 to do the work with, but I could not find any procedures in either the Instruction manual or the service manual.? Perhaps I overlooked it.?
?
Thanks!
Jeff KC8VFN
