MSF 5000 low pass filter question

d119 · Post by **d119** » Thu May 11, 2006 11:37 pm

Recently purchased a 403-435MHz MSF 5000 repeater station. Radio tuned up fine on the 447MHz channel I wanted it to be on. 100W output and .4uV RX Sens. Not spectacular on receive, but usable.

The station had the internal duplex (Pre & Post & Tee cable) filter option. The filters DID NOT tune to 447MHz successfully.

I have a friend who is using an MSF 5000 as a 420MHz link radio, and his station does not have the internal duplex option. I am going to give him my internal duplex equipment in exchange for his external duplex equipment so I may put an external duplexer on my MSF 5000 and use it successfully on 447MHz by way of a T1500 series duplexer.

The question I have, is that his 403-435MHz station with external duplex has a low-pass filter in it on the transmitter side. It's a tube shaped thing with N connectors on either end.

Will this low-pass filter work in a 447MHz station, or is it band-specific to 403-435, like the internal duplex stuff I tried to tune?

I am ASSuming it is frequency-specific, but would like some outside input on the subject.

Thanks!

kcbooboo · Post by **kcbooboo** » Fri May 12, 2006 3:23 am

The low pass filter is not listed in the freq-dependent chart. I have one on my base station and it has a very nice cutoff frequency of about 600 MHz. Since it just has to knock down the 2nd and 3rd harmonics, there's no need for it to be frequency dependent.

The internal filter/duplexer could be, but I couldn't find it listed in any of my manuals. I know that the TEE cable IS frequency-dependent and also specific for the TX/RX relationship. There are six variations to the cable.

I'll look around again for info on the filter/duplexer - I know I have it somewhere - and let you know if it's freq-dependent. Since the front end preselector on the RF tray IS freq-dependent, I'd suspect that the filter/duplexer is also.

Bob M.

Doug · Post by **Doug** » Fri May 12, 2006 5:07 am

Good Morning Bob and d119,
I did some digging around in some of my MSF manuals with regards to the transmitter filtering and I found three different filter combinations in the UHF range.
TFE6491A - 403-435MHz with 5-20MHz T/R separation
TFE6492A - 435-475MHz with 5-20MHz T/R separation
TFE6561A - 403-435MHz with 3-20MHz T/R separation
Combining TEE,
TLE5721A - 403-435MHz (red) T below R, 3-20MHz
TLE5731A - 403-435MHz (pink) T below R, 5-20MHz
TLE5732A - 435-475MHz (green) T below R 5-20MHz
TLE5771A - 403-435MHz (gray) T above R 5-20MHz
TLE5772A - 435-475MHz (yellow) T above R 5-20MHz
TLE5781A - 403-435MHz (orange) T above R 3-20MHz
I haven't found anything on the pass filter, so I guess I'm with Bob on this one that it isn't frequency dependent between the two ranges
Enjoy the day
Doug

kcbooboo · Post by **kcbooboo** » Fri May 12, 2006 5:35 am

The TEE cable info is in the MSF5000 photo tour. I just couldn't find the proper section of my manual to come up with the info Doug posted.

I suppose if the part number on the low pass filter ends with a 1 or a 2, it would be band-specific; otherwise not.

Bob M.

d119 · Post by **d119** » Fri May 12, 2006 11:42 am

Well the filter I took out of the station is a TFE6612A.

I'll put the low pass filter from the 403-435MHz station in my station so it's there.

Thank you for the info!