PAC-RT crystals and alignment

[ke4zdg]

I just got a UHF PAC-RT (model XH14TTY3110A) and connected it to my Spectra. Last night, I finished working out all the hacks I had to make to the Spectra drawer and control head. The PTT, receive and transmit work flawlessly now.

The next step is to recrystal it. After giving the radio board a good inspection, I only found one crystal on it.

First question, what's the formula for the crystal calculation? On batlabs, I found the formula for RX and TX crystals. The PAC only has one crystal (I'm assuming for both RX and TX). Which formula should I use? I want to crystal it for somewhere around 446-447 MHz.

Second question, what sort of alignment procedure do I need to go through? I have an IFR service monitor on loan (from a friend).

Third question, does anybody have a copy of the service manual scanned I can download?

Thanks,

Jared

[George]

Jared,

What you have there is the basic MH-10 portable radio with a pile of logic around it.

You do have two crystals, but the transmit one is inside of a resonator and the other is just a bare crystal.

Your best bet is to call International and send them the resonator and they will handle everything for you. Just tell them what freq you want and they will do the rest.

As for alignment, that can get entertaining. Providing you are not moving the thing monumentally out of the range, you can tune up without any parts changes. I moved mine to 446.9 without a problem.

I suggest you mark the rf board with a fine point Sharpie with the T or L number for each slug. It will make alignment much easier. Don't expect anything over 250 or 300 MW out also. Sensitivity should be acceptable in the under .4 area. Also, be careful with the alignment tool as you are dealing with OLD slugs and forms.

There isn't a test set for this and if I remember right, which I am half asleep now anyway, you have to use a VTVM or an RF millivoltmeter to do the alignmenet. I don't remember, but it was not THAT difficult.

Manuals will show up eventually and I may have one on the shelf but I don't know at the moment.

Have fun, you bought yourself a nice project.

George

[d119]

There isn't a test set for this and if I remember right, which I am half asleep now anyway, you have to use a VTVM or an RF millivoltmeter to do the alignmenet. I don't remember, but it was not THAT difficult.

George

There *IS* a PAC-RT test set, I have one at work... I'll take a look in the next day or so and get a part #.

[George]

I think the test set you are thinking of is the one that allows you to test without a mobile radio being attached. It lets you work on the PAC-RT alone.

If I remember right, that test set does not allow metering of the alignment points on the radio portion of the PAC-RT. It's for injection of noise and power and such.

But then again, I never used one because I followed the alignment instructions in the manual and I don't think it mentioned the test set.

Since I am asleep at work anyway, I could well be wrong so nothing matters and what if it did because I am still getting a paycheck.

George

[ke4zdg]

I have an IFR service monitor and a DMM, so I don't really need a test set. I'll probably just rebuild the resonator myself instead of sending it away. I've done it with Mitreks before.

I sent an email to Bomar, but didn't get a response. I'll try International next.

Those powerout specs are perfect. I just want to use a PAC to kick around the house with an HT. Right now it works perfect with my UHF Saber set to super-low power out.

Please let me know if anyone finds a manual they can scan and email.

[wa2zdy]

I sent an email to Bomar, but didn't get a response. I'll try International next.

Forget Bomar. Their stuff is not known for high quality. ICM is the only way to go. Lifetime warranty too. All you need to tell them is what equipment you have and what receive and transmit frequencies you want. They have the tech info and take it from there.

[ke4zdg]

Ok. I got my crystals in from ICM and installed. The PAC-RT's receiver is working great, but the transmitter is way out of alignment. If I hold my Saber's antenna right against the PAC-RT's antenna I can faintly hear it. Anybody know which coils/pots/caps I need to fiddle with. The radio board has like 20 little things to turn, and I don't want to jump in and turn random screws.