Maxtrac Transmitting Poor

motofreak008 · Post by **motofreak008** » Thu Feb 22, 2007 8:09 pm

I have a VHF Maxtrac 100. Up until Tuesday I had it hooked up to a Hustler cell phone antenna. The antenna worked with out bag phones when we had them. Now I have a VHF 1/4 wave antenna installed on my pickup. I have a coax adaptor for it.
Now, my problem is that when I had the cell phone antenna, I got better range. I don't have the best range, but I had better range with the cell phone antenna. Why is this. I am transmitting it to a P50, could that not just be picking it up? The antenna is located just behind the drivers side on the front of the box barely clearing the roof and just one inch behind the cab. Should I find a new place to locate the antenna? The thing about the antenna location is where I was transmitting to was behind me, so the cab was not obstructing the waves. This has got me stumped, I don't think it has the model # tag on it so I am not for sure of how many watts it is transmitting on. Any help would be appreciated. I am just very confused at the moment.

thebigphish · Post by **thebigphish** » Thu Feb 22, 2007 8:42 pm

wait, am i reading this right? You had a VHF radio on a cell antenna? And now you have a VHF 1/4 wave on the same VHF unit? And you are having problems with it? yes?

motofreak008 · Post by **motofreak008** » Thu Feb 22, 2007 8:53 pm

Yep, I didn't have a VHF antenna when I installed the radio and wasn't for sure at the time it it really mattered on a mobile radio.

57Shasta · Post by **57Shasta** » Thu Feb 22, 2007 10:16 pm

Time to break out the Bird 43. Betcha he crimped the mini UHF with vise grips!

Post by **wavetar** » Fri Feb 23, 2007 5:35 am

Without any sort of equipment to actually test if you have a working mobile & portable, it's difficult to say. Also the fact you didn't know hooking it to a cell antenna was a bad thing tells us the VHF antenna install may not have been done properly as well...whip not cut properly, connectors not crimped properly, etc.
It's probably worth your while to pay the 1/2-hr or 1-hr charge to have a shop look at it & tell you what's wrong.

Todd

motofreak008 · Post by **motofreak008** » Fri Feb 23, 2007 5:51 am

First of all, no crimping was done with the install, and I know better than to crimp any wires with vise grips and have never done so. I wasn't born yesterday. I didn't ask to be made fun of, I asked for help.

Did I hurt the radio by using the cell phone antenna? If so, how does that hurt it? Like I said, that was the only antenna I had and I wasn't for sure if it made a difference at the time. I know now the difference in antennas and am learning now to always use the right antenna. With that said, what is wrong?

Terry_Glover · Post by **Terry_Glover** » Fri Feb 23, 2007 6:13 am

Plain and simply, it's called antenna mismatch. It amounts to high SWR, reflected RF energy, and other factors that will damage a radio.

Sounds like you may have damaged <u>your</u> radio.

k2hz · Post by **k2hz** » Fri Feb 23, 2007 6:19 am

If you just used the cell phone antenna for receive, no harm would have been done. Transmitting on the cell phone antenna would have possibly damaged the power amplifier.

It really sounds like a problem with the antenna installation which is best checked with a wattmeter which would also tell you if the TX RF output is still ok or there was damage from operating on mismatched antenna.

If you did no crimping, how did you install the antenna connector? If it was a solder instead of a crimp type, a common problem is the insulation melted from improper soldering or the connector is shorted due to improper coax stripping and preparation.

phrawg · Post by **phrawg** » Fri Feb 23, 2007 6:26 am

Well...... Help we are trying to do. but .....

Yes, the antenna cut for 800 mhz could very well have blown the
pa on the mobile radio. Now you have little or no power out.

The one inch from metal truck cab is also a no-no. A vhf antenna
needs a clear 18 inches around it or it is just like the 800Mhz
antenna as far as the radio is concerned. (possible fried pa),
not to mention it cant radiate when it is shielded like that. it
cant radiate even if thete was no radio damage. By crimping
we dont mean not pinching the wire under a seat bracket etc,
we mean the method of attaching a proper connector with the
correct tool to the coax. At this point a shop is strongly advised
for the purpose of determining what if any of the equipment
you have is still intact and in specs. Then let them properly
install it ON THE ROOF TOP ! BTW, just curious as to how
you are using this pair and what service it is licensed in.
This issue may make the whole point of this install a moot
point anyway as the fines for unlicensed operation are
pretty stiff. Phrawg

motofreak008 · Post by **motofreak008** » Tue Feb 27, 2007 8:17 pm

How hard is it and is it possible to change out the PA? What if I would install the antenna in front of the cab by the hood? Would that work? My father's workplace does that with there antennas. I really don't want to drill a hole the roof of my pickup if I don't have to.

jackhackett · Post by **jackhackett** » Wed Feb 28, 2007 11:06 am

The PAs are easy to replace, take the covers off the radio, disconnect the three cables connecting the PA to the RF and logic boards, take out two bolts and off it comes. Slap another one on, go through the alignment in the RSS service menu and that should do it.

They make a little L bracket for NMO mount antennas that you can mount in the gap between the hood and fender, you need to put two screw holes in, but they're down inside where they won't show when you take it off to trade in the truck.

motofreak008 · Post by **motofreak008** » Wed Feb 28, 2007 5:45 pm

Forgot to ask and it may seem obvious, but I just want to make sure. If I get a PA, I need to get a VHF PA right? Or does it matter? I think that it would, but I just want to check.

ard099 · Post by **ard099** » Wed Feb 28, 2007 7:21 pm

Don't worry about replacing the PA deck yet, it may not be necessary, and it is the most expensive route you will take, if you want a new pa. What you need to do first of all is check the antenna cable. Get a multimeter, put it in the ohms position. Disconnect the antenna cable, and the antenna rod from the other end of the coax. Take one lead of the multimeter and put it on the center pin of the connector, take the other lead and put it on the outside of the connector. You should read a high resistance, or see no change on the meter, if the connector or cable is shorted, you will read a short, or low resistance on the meter, like touching the two leads together. Another check is to check continuity in the coax. Put one lead on the center pin of the connector, and put the other lead on the center of the ant bushing(the part where the ant rod screws to). You should read a low resistance, indicating that you at least have continuity. Do this for the outer(ground side) also. These are just easy checks that you can do yourself without having to pay someone to look at it. The ant connector is usually the cheapest part, but it is probably the most critical, and the easiest to screw up. If you cant figure it out you may have to take it to a radio shop and let them take a look at it. By the way, how far do you need to talk?

Bat2way · Post by **Bat2way** » Wed Feb 28, 2007 8:47 pm

Dude...this isn't slapping you down, but, you aren't qualified to be messing around with this radio. Back in the day, this is the reason you HAD TO HAVE at least a 2nd Class FCC ticket to work in radio as a technician. Just take the radio somewhere to get looked at. You'll save $$$'s rather than butchering it, then throwing it away.

kc7gr · Post by **kc7gr** » Fri Mar 02, 2007 10:18 am

Bat2way wrote:Dude...this isn't slapping you down, but, you aren't qualified to be messing around with this radio. Back in the day, this is the reason you HAD TO HAVE at least a 2nd Class FCC ticket to work in radio as a technician. Just take the radio somewhere to get looked at. You'll save $$$'s rather than butchering it, then throwing it away.

I have to agree. Your earlier posts, indicating that you didn't think using an 800MHz antenna for a VHF radio would matter, say a great deal to more experienced ears.

There is another concern. Physically replacing the PA on a Maxtrac is only Step 1 in the process of repairing a damaged unit. Since each PA is a little different, in terms of manufacturing values and tolerances, you will need to go through a full PA alignment procedure once the PA section is replaced.

This will require several things, including the proper radio service software, a computer to run it, the right programming cable and RIB, and (most importantly) a service monitor. You will also need the knowledge to work with all the above.

Based on your earlier posts, and your subsequent questions, I would strongly recommend that you seek out the assistance of a professional technician. Watch over their shoulder, if they'll let you, and learn, but my current guess is that you do not have the proper test equipment or the necessary experience, to make sure that your radio will operate to spec once the repairs are completed.

Ignorance is nothing to be embarassed about. None of us learned what we did overnight. The only Bad Thing is if you refuse to learn from your errors.

Happy tweaking.