MSF5000 channels

srefurd · Post by **srefurd** » Fri Aug 22, 2003 6:53 am

This might sound stupid BUT:

What is the purpose of having multiple channels in a MSF 5000?

If your receiver is tuned and with all of the filtering on transmit can you actually put different freqs in the radio? Or is it that they just have to be so close together within X of a center freq? I have read about how tight the front end is. It just doesn't make a whole lot of sense to me.

TIA
R

Andy Brinkley · Post by **Andy Brinkley** » Fri Aug 22, 2003 9:16 am

The number of channels available depends on which (tone or dc) control card is present.

Many of the MSF-5000's are setup as multi channel full duplex base station with the control operator being able to change channels via the remote.

I have also seen MSF-5000's set up as a repeater with all 10 UHF MED channels so that the dispatcher can select which MED Channel to bring up for the EMS units to talk to the hospital. Certainly it is cheaper than 10 dedicated repeaters.

srefurd · Post by **srefurd** » Fri Aug 22, 2003 10:46 am

OK so how far apart can the frequencies be? I'm thinking that there have to be some limitations due to the selectivity of the front end? Are there any restrictions? As far a channel spacing etc.

Nand · Post by **Nand** » Fri Aug 22, 2003 11:04 am

Both the VHF and UHF MSF5000 have RX bandwidth of 2 MHz.
The TX bandwidth for VHF and UHF is 26 and 8 MHz respectively.

The quality of the receiver is also determined by the mixer spurious response, the IF selectivity and the purity of the injection oscillator signal.

Nand.

ASTROMODAT · Post by **ASTROMODAT** » Fri Aug 22, 2003 8:53 pm

If the MSF-5000 is configured as a repeater, the biggest limitation on bandwidth, from a systems standpoint, would likely be the duplexer. For instance, at UHF frequencies, you'd likely be limited to about 600 kHz of bandwidth, so you could move plus/minus 300 kHz from your center frequency, before suffering substantial degredation in performance.

Larry

kd6kml · Post by **kd6kml** » Sat Aug 23, 2003 12:22 pm

My MSF is going to be a backup station that I will take where it is needed. I plan to program my station with the tones that are used at each of my sites (same RF channel) so the radio can be moved if necessary and be programmed correctly. I also might put in our ham channels i nthe event I want to retune and use it for that purpose.

That is one use I see for multiple channels in a repeater mode, even if changing channels means tuning the station.

Josh

bernie · Post by **bernie** » Sun Aug 24, 2003 11:45 am

My two bits worth:
There is no great problem running a multi channel repeater on a site:
A ferrite hibred combiner dosn't care about frerquency spacing, then one could also use a seperate antenna for transmit.
Obviousley there are other concerns about interference with other equipment on the site.

srefurd · Post by **srefurd** » Sun Aug 24, 2003 12:23 pm

IF (big if) I understand correctly then basically the MSF has a duplexer it is just split in to two parts. (I realize that is an oversimplification bear with me) The receive side of the duplexer is actually part of the rf tray correct?

The transmit side of the duplexer is the pre and post filtering for the Amplifier, correct?

So if the above suppositions are true then what would be the maximum spacing for your transmit frequencies, and separately for your receive frequencies?

Andy I understand about the 10 med channels. My question is how much of a spread was on the channels? And did the system use the stock /\/\ filters or was there an aftermarket duplexer?

Nand if I understand you correctly then for UHF transmit of 8 Mhz and receive of 2 Mhz. Is this the base station setup or repeater with the filtering?

Bernie I somewhat understand about using combiners. Problem is this is going up my own tower, alone. I see no need to invest the kind of money a combiner would run. I was just wondering about the ability of the UHF MSF to run multiple frequencies, and how far apart they could be.

Again thanks Guys
R

Nand · Post by **Nand** » Sun Aug 24, 2003 1:58 pm

srefurd wrote:
Nand if I understand you correctly then for UHF transmit of 8 Mhz and receive of 2 Mhz. Is this the base station setup or repeater with the filtering?

What this means is that once tuned for a specific frequency, you can change the TX frequency +/- 4 MHz without retuning the TX VCO and you can change the RX frequency +/- 1 MHz without retuning the complete receiver. It may actually work outside these limits, but if you do the station may not meet the specifications as listed in the manual. This does not have anything to do with it being used for a base or repeater.

Again, as for the MSF having a tight front end for a receiver, it uses 5 or 6 relatively large cavities for a receiver, this makes it a lot better than mostly anything else out there. There are configurations that have a similar additional filter for the TX side. In these cases, with a wide enough split between TX and RX and no to much power, a duplex is not needed. My manual refers to a “post filter” in the TX output that takes the place of the existing low pass filter. No other details are given.
I believe XMO and Will described this filter not long ago. Chances are that you won’t be able to get one of these any longer.

http://batboard.batlabs.com/viewtopic.p ... ht=msf5000

Nand.

ASTROMODAT · Post by **ASTROMODAT** » Sun Aug 24, 2003 3:36 pm

If someone is after a wide spaced repeater, then they might want to consider a Quantar.

The TX is good for the entire 438 to 470 MHz band.

The RX is good for 4 MHz of bandwidth within the 438-470 MHz Range 2 band. In addition, you can get an additional 4 MHz of receiver bandwidth (contiguous or not, user's choice) by simply sliding in the optional second receiver.

Problem solved, and you get full performance specs (no duplexer, of course). And, the gravey of this solution is that you are ready for ASTRO 25. Bit more pricey than MSF 5000, though.

Larry

srefurd · Post by **srefurd** » Sun Aug 24, 2003 4:01 pm

Will wrote:
"In the UHF MSF5000 the duplexer consists of a T connector with three cables and the connectors to go to the output of the transmitter filter and the receiver frontend filter and the antenna port."

here: http://batboard.batlabs.com/viewtopic.php?p=20868#20868

This is what made me think of a "split duplexer" also XMO stated:
“The receiver preselector has enough selectivity to serve as part of the in-cabinet duplex option in combination with additional transmit filtering and a special duplex phasing harness.”

here: http://batboard.batlabs.com/viewtopic.php?p=86792#86792

That's why I ask about the difference between the base station and repeater. My unit is/was a base station. I lack the transmit filter section. (As well as the matching harness)

If the receive section is +\- 1Mhz it wouldn't matter if base or repeater as this is the same for both types of units. However if configured as a base station there are some differences as pointed out in the topic you listed.

What I was wondering was if equipped with the original /\/\ filter equipment for a repeater what would the frequency spread be?

As I noted above the specs for the receiver would not change, however I am wondering what that would do to the transmitter specs.

Reason I am asking this is I am in the process of installing a MSF for GMRS. I am wondering if it would be worth the aggravation of finding a set of transmitter filters to be able to use more than one GMRS repeater pair.

No offense Larry, but some of us are poor, and some more of us are REALLY POOR. I fall into the later category. I am going to have my repeater on the air INCLUDING erecting the tower for less than a used quantar!

Will · Post by **Will** » Mon Aug 25, 2003 1:08 am

Somewhere I have the measurements for the "T" cable for UHF. The receiver will go the 200khz needed for all the GMRS rptr inputs as will the transmitter. I removed the noise generating and very lossey circulators from all my MSF500's PA's and only had to run the harmonic filter on the output of the PA going into the "T" connector . The factory transmit filtering was done between the IPA and the PA with a three stage helical filter. One could use a small cavity filter between the IPA and PA or even on the output if the transmitter makes enough noise in the receiver, but most MSF5000's are fairly quiet on transmitter noise. Anyway at GMRS you are only running 50 watts out of the "T" connector so the PA is loofing!!!!. BTW our 5000's are running Zetron M38SP's for the different tones and DPL's.

Big Towers · Post by **Big Towers** » Wed Aug 27, 2003 10:37 pm

If you need the "T-Connector", I can send you one for price of shipping. I cannot stand the "insertion loss" of the Motorola TX part of their "duplexer". I have also found that the internal "duplexer" does not provide easily for a preamp install, and isolation wise is not good enough either.

In all the MSF repeater stations I have on UHF, the internal "dupolexer" has been removed opting for a good Celwave external duplexer. A bunch more power to the antenna and more than enough isolation to run a gaas fet preamp without desense. I know that I have at least one of the T harness laying around, and I know I have one in a station that has not been converted to external duplexer yet.

MSF5000 channels

MSF5000 channels

MSF-5000

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