This is a mod to replace XF-6 IF crystal filter with an eight pole 2.1 Khz. International Radio unit. Their # for the filter is #92 and it is also used in the TS-50.
Began by removing the bottom cover of transceiver and then remove the seventeen screws which hold the rf circuit board in place. Also remove the clip from IC9 near edge of board. There is no insulating material here. There is one rf coax connector near the rear of board that has to be unplugged to raise and flip over circuit board. Be sure to mark where this connector is as there is an unused one nearby.
XF-6 is clearly labelled and is chrome plated. Using a small isolated tip soldering iron and small solder wick clean solder from the four pins and two mounting ears of XF-6 then gently remove it. Using small coax (I found some .045 teflon) or the supplied RG-174 remotely mount the filter. Since the original filter uses .01 micro farad coupling caps none are required at the filter.
I mounted mine on the double sided tape pad where the voice chip mounts as I'm not using one. There is ample room near the fan area also. The other thing I did was to peak the IF inductors L69, L71, L87, L613 and L614. All of these inductors are labelled on the circuit board. Inject a signal at hf frequency and using an oscilloscope or AC millivolt meter across the speaker leads peak these inductors for maximum output. Set the injected signal and audio
control for a good meter reading before starting to adjust. Always remember what position the tool was in before any adjustment is made in case of error. One can use jewellers screwdrivers for adjustment tools.
Peaking up these IF inductors helped the receive level on my unit.
On the air tests came back with excellent Kenwood audio on both side bands. Results were very pleasing with the IF crystal filter change. For those who say this transceiver suffers from filter blow bye this may be a good mod. It does not deter from the excellent audio this transceiver has on both receive and transmit. My Kenwood filter is at International Radio for sweep test versus their replacement and I'll post the results here. Wilbur wilby@pix.net has an operating manual for this radio on CD for a great price and it's printable. There are small components in this radio and exercising care while doing this mod is very important. I claim no responsibility in someone else performing this mod with disastrous results.
As is evident by the filter sweeps George W2VJN of International Radio did on my original filter versus his there are obvious advantages in this modification.
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