MSF5000 900Mhz Mods

[KD4GPI]

I just got 5 C85GFB5203AT's. These are the trunked versions. Is there anything special that needs to be done to make these work as conventional repeaters on the 900Mhz band other than programming/tuning?

Thanks,
KD4GPI

[batdude]

nope, just create a new codeplug from the templates included in the MSF software and blast it.

it'll tune right up.

doug

[MSS-Dave]

nope, just create a new codeplug from the templates included in the MSF software and blast it.

it'll tune right up.

doug

Doug...

Will the MSF RSS allow programming into 902/927 on the GFB model without mods or not? My C85CLB went right there using the R1801 and disabling range checking.

Thanks.

Dave

[batdude]

i think it gives you the "ARE YOU SURE" messages when you enter the out of band freqs...

it complains, but it takes it

just stay at the 902/927 split - i wouldn't go far from there



doug

[KD4GPI]

Thanks Doug. Georgia uses the 25Mhz split so that won't be a problem.

Thanks again for the help.

Jeff

[motor59]

OK, I'm going to jump in here with a MSF5000 newbie question.

First off, I want to make it clear that I know diddly about this line of radios.

However, I have a line (a VERY thin line) on a ton of trunked 900 MSF's.
(Actually, as much as they weigh, I have a line on about 31 tons of them...)

I'm told that they aren't going to do anyone much good, since they were used on a trunked system that used a rubidium (sp?) timing standard. They apparently are missing a reference oscillator necessary for standalone operation, and the cost to retrofit each one is way beyond their value as 10+year old units.

Any comment?

[batdude]

true sorta

without a high stability timing reference, your digital 900 tray will not function as it uses this timing for the basis of operation for the whole station.

i betcha if you look at each and every one of these stations, you'll find more than one that still has the high stability oscillator in the bottom of the cabinet.

of course, if you CAN'T find one with the oscillator, watch ebay - they show up occasionally.

yes, they are like $5000 from motorola.

if you have unrestrained (and unlimited) access the the stations for parts, there are tons of hams who could use the PA and circulator setup for 900Mhz projects. the msf PA shelf is the most rugged and longest lasting shelf around- the "high" power 900 units @ 75w last forever. 150w units use a driver and final PA - each the same size...

if the control shelf is a digital with the 3 digit LED display then that board too is useful as it can be reprogrammed or modified with little effort to work on other bands (VHF/UHF) - there might be a few component differences, but a new codeplug results in correct operation 99% of the time (i've done a 800 Mhz to UHF control shelf conversion with no problems)

bernie here on batlabs is by far the expert on the MSF here.


doug

[KD4GPI]

I need to look at the docs but if the MSF is just looking for the 10 Mhz ref, any high stab ref osc will work. A Quantar can be told what to look for through the RSS.

[ASTROMODAT]

There is a Ham in the Seattle area who has a large number of MSF 5000's on the 902-928 MHz Ham band. He has a number of simulcast Transmitters (using GPS for sync), and a ton of voting Receivers. Seem to work quite nicely. His 900 MHz machines are also linked to his network of 440 MHz MSF 5000's.

larry

[kcbooboo]

The 800 MHz units can work with an external reference, but I don't think it's a common simple frequency; something like 14.4 MHz. I have the manual for the VHF/UHF/800 models and very little is mentioned about how to hook up the external reference, besides where to get power for it. Even the input on the RF tray, from this reference, is not specified.

While there are a few differences in the 800 MHz SSCB units, the major ones are the addition of a "flutter-fighter" for 800, and possibly narrower bandwidth for transmitted audio. I don't have a 900 MHz manual available so I can't tell you much about those units.

Bob M.

[MSS-Dave]

I need to look at the docs but if the MSF is just looking for the 10 Mhz ref, any high stab ref osc will work. A Quantar can be told what to look for through the RSS.

Not 100% sure without the manual but the MSF with external oscillator option should be looking for 5 MHz (at least on 900 MHz). 800 and other bands will have a internal reference unless optioned for simulcast.

Dave

[bernie]

My two bits worth:
I am on vacation, and do not have manuals for 800 or 900 simulcast stations.
In my limited experience with stations that require external reference I recall there is some sort of oscillator such as a Rubidium with a 10 Meg output.
This feeds a sythensizer that runs at 14.4 Meg.
The chassis looks like the UHS PURC/MSF/Micor synthesizer.
This feeds a multicoupler that feeds 14.4 to each station.

Perhaps the UNI board has the foil pattern for a 1ppm oscillator such as in the 800 stations.
The parts could be salvaged from an 800 board.
You should be so lucky if you had a UHF station the old 2PPM 14.4 channel element is left in place, several small components clopped from the standard board. It might be worth a look.

If a lower stability is acceptable, or for testing you could use a radio with a 14.4 Meg reference, and connect the radios oscillator to the ext ref jack on the station. I recall this is a BNC.
The input to the RF tray is on the right side. There are 2 RCA plugs, one marked REF IN.
I have an old "A" 800 analog board which was replaced in a mandatory update program.
I use the 14.4 oscillator to provide the 14.4 reference for the UHF ext reference stations that come to my shop for repair.
All I have to do is provide 9.5 volts to the proper traces and tacked a RCA
cable to the reference output on the board.

[ASTROMODAT]

There was recently one of these external reference oscillators on eBay for the MSF 5000. I think it was like $9,000 new, and it sold for a few hundred bucks. You might want to crusie around eBay for another unit.

larry

[n8obu]

i have any parts one could need i run these on vhf / uhf and uhf high 900mhz they work great just keep the power at /or lower than its rated output if one runs one on uhf /440 there is a mod that one should do that keeps the 5 mhz ref from mixing with the out put and ending up on your input if you run a + offset and on 900 mhz let them warm up for at least 1 hour to settle down on freq and 24 hour befor fine tuning them , i am skeaking of the high stab units

[MSS-Dave]

if one runs one on uhf /440 there is a mod that one should do that keeps the 5 mhz ref from mixing with the out put and ending up on your input if you run a + offset

Ummmm.... can you help me on this one??? I've worked on UHF MSF for years and I've never had any problems with the reference mixing with the TX (well, the internal reference anyway, never used external on UHF). TX is low and RX is high. Used them from 443 to 465 on TX as well.

Dave