UHF MSF IF freq shift

[e.field]

Does anyone know if the IF frequency can be change to 10.8 MHz? I recently added another channel to one of my LTR sites and the new recieve frequency is 10.7 MHz below one of the existing rx frequencies, so I am getting interference on the rx of the new channel from the rx VCO of the existing repeater(also an MSF). Any ideas?

Thanks,
Eric

[kcbooboo]

I didn't see anything about shifting the IF in the RSS manual, and since the programmed frequency would be different to accomodate that, I'm now going to check the hardware manuals.

A Micor receiver (i.e. Spectra-TAC) has an 11.7 MHz IF, but it uses channel elements. The alternate IF is 11.8 MHz, and the manuals tell you what to change in order to get that.

I'll get back here if I find anything, but somehow I doubt it. Bernie will likely chime in here if he has any info.

Bob M.

[kcbooboo]

I saw no official option for shifting the IF, nor any notes or alternate parts in the manual. I think you're stuck with this problem if you use any radio with a 10.7 MHz IF.

Something's got to go !

Bob M.

[e.field]

Thanks for your replying to my post. Looks like I will replace the MSF with a unit that has an IF other than 10.7 MHz.

[Will]

I know there is a shifted IF kit for the MSR2000 aka Mitrek receiver. Maybe those filters may work in your MSF. Program your MSF receiver .1mHz lower, should work.

[xmo]

Will's suggestion should work. The 10.7 crystal filters used in the MSR2000 have the same part number as those used in the MSF5000 [9180011E05], hence it follows that the MSR2000 10.8 MHz parts should work in the MSF.

Now all you need to do is FIND them [4884396K06 NLA]

[Nand]

Here is an alternative that may work for you depending on the RX frequency of the station that causes the problem. If you are past the hardware limits of the station, it likely will not work.

Reprogram the RX frequency for this station that needs to operate with a different VCO frequency 2 times the IF frequency higher (21.7 mHz). This should let you receive the image frequency ( the same as the present RX frequency). The RSS will warn you that this may be out of range, but it will let you do this.
If it works, you will need to tune the VCO and the injection coils L7, L8 and L9 as per manual. The front end should not need any tuning.

Nand.

[kcbooboo]

I think you mean 21.4 MHz higher (2 * 10.7). This will make it do high-side injection, and if it tunes up there, it will certainly get the receive VCO off your other frequency.

Bob M.

[e.field]

Thank you all for your replys. I found a VHF MSR2000 receiver that was in a station with two receivers that had a 10.8 MHz IF. Swapped the IF filter xtals into the MSF. Burned a new prom with the receive frequency 100 KHz lower. Works like a champ. Thanks again for your help.