MTS-2000 Bad RX/TX

[kb1nbn]

Hello all,



A little while ago I purchased an MTS-2000 III VHF Flashport radio off of ebay... Model H01KDH9PW1BN After programming it, I noticed that the RX and TX really didnt work nearly as good as they should have... I tried multiple antennas and batteries with no luck... The frequency I was testing with was a Ham radio Simplex Frequency in the 146 freq range... It also wont perform on my fire department's frequency's either...


Any help would be great

[Will]

Step one, check the antenna connector from the RF board to the antenna connector. Also the antenna switch for the MTVA could be bad.

[MTS2000des]

my question is did the radio work properly BEFORE programming? if so could be a bad codeplug? did you use CPS/RSS or force a codeplug in some other way without retuning?

As Will said, the weak point on the Jedi's is the RF switch. I had one go bad and develop a hairline crack on the little gold contact inside the switch that slid back and forth and switches the actual hot side of the RF out from the side connector to the antenan ferrule. The radio had very poor TX but RX worked, but not as good as other radios. Good thing I checked it, as it saved hosing the PA. It's no wonder they moved the switch to an external connector on the XTS series, these RF switches are a poor design and don't hold up well with alot of use (e.g, taking them in and out of an MTVA, connection and disconnection of public safety RSM, etc).

[kb1nbn]

Well, the radio came with just a bunch of random stuff programmed in it however, I do remember pulling out a freq. counter and finding what freq was programmed into it, it was simplex and I was able to receive from the other side of the room...


the radio TXs and RXs but The signal cant be received more than 30 feet away...

[AEC]

If not the switch, possibly an alignment issue with the VCO crossover frequencies for his version of RF board may be incorrect, causing a loss of high end frequencies, as a 'K' version radio should be easily able to get to via RSS or CPS.

I'd run it through a service check, then cross reference the VCO crossover frequencies with the model number of the RF board it has.

Odds are, both are incompatible, or the crossover point have been changed by someone that had no idea what the function of the crossover frequencies accomplish in the Jedi series.

[fineshot1]

The power amplifier rf power output needs to be checked using a service monitor or watt meter
and the rx sensitivity needs to be measured as well. Sometime when the power amp brick goes
bad in these radios it also takes out the rx side with a almost short circuit on the output taking
out both rx & tx.

EDIT: FYI - the radio will still put out power in the milliwatt range and at close range without
a power output measurement it seems ok on tx.

[AEC]

EDIT: FYI - the radio will still put out power in the milliwatt range and at close range without
a power output measurement it seems ok on tx.

As you stated above, the P.A is making power, but not at the level it is designed to produce, so I would check current drain in TX, and then decide if a replacement P.A is worth the cost, not to mention that removing one of these is a major PITA if you do not have the proper hot air reflow station, or the ability to remove the P.A as the blank is soldered directly to the board with several solder pads and it takes some real heat to remove it.

Returning to the actual trouble here; if the P.A is drawing some hefty current without the respective outut power, then the amp is dead.
You may have a couple of stages operational, but that is of no use when you can't make rated power for the current draw.
Not to mention the posibility of self oscillation/excitation of the module itself due to internal heat stress already present within the module.

Before diving head first into a repair, check the pins of the module first, to make certain they are not loose from over current draw, or simply a poor/cold solder joint.

There are also two PIN diodes on the board, near the top, D118 and D119, these are for switching from RX to TX and do not function until they are forward biased in their respective 'modes'. These diodes are small white rectangles with the bands facing each other-you can't miss them as they are right under, and slightly to the right of the alignment hole/slot(depending on the date of Mfg.).

u------ 'u' indicates alignment slot/hole.
[ ] [ |] [| ]<---PIN diodes
cap pin pin (pipe indicates cathode)


I sure hope THAT comes out on posting!