I want to ask what may be a real dumb question

Post by **KG4PSN** » Tue Oct 21, 2008 7:58 pm

so here goes:
on a motorola xts 5000 UHF HI, will the transmitter section
be damaged at all if I were to use a completely different
band antenna?

i already know that reception will suffer, but i really want to put as stubby an antenna
as i can find, even if it's not the correct band antenna. i was told that this would indeed
damage the transmit section, but i wanted some more opinions...

don't ask me why i want to do this! but if you must know my reason, it's just that
i really dislike any sort of tall antenna... so we don't need to examine correctly banded
antennas, i just would like to know if using an incorrectly banded antenna will hurt the
transmit section... sometimes i want to try to take a double ended sma connector
and use my ham stubby's as well....

tvsjr · Post by **tvsjr** » Wed Oct 22, 2008 3:48 am

Yes, you may well damage the PA. It has internal circuitry to protect itself, but that's not foolproof.

The more pressing issue is that it simply won't work worth a damn. One would assume that, if you are transmitting, you probably have a legitimate reason to do so. If you use an improper antenna, the PA will fold its output power back due to the mismatch, and your radio simply won't work well. A typical UHF whip is, what, 5" long? Deal with it.

Using an adapter is a bad idea - the Moto connectors are built where the plastic "sheath" around the connector contacts the case of the radio, providing physical stability and a seal. By using adapters, you subject the connector in the radio to lots more abuse, and diminish the water resistance of the unit.

In short... suck it up and deal with it, and be thankful you don't have to use a wide-band VHF whip like many of us do (9" long and inflexible).

Post by **KG4PSN** » Wed Oct 22, 2008 6:52 am

excellent answer, and indeed i wiil get over it!

thank you

W2MB · Post by **W2MB** » Wed Oct 22, 2008 7:14 am

Pretty basic, a non-resonant antenna is not good. I would think that you would of come across that somewhere in exam theory for the license you hold.

Post by **escomm** » Wed Oct 22, 2008 8:51 am

OEM UHF stubby antennas are about $20

motorola_otaku · Post by **motorola_otaku** » Wed Oct 22, 2008 9:51 am

escomm wrote:OEM UHF stubby antennas are about $20

..and are all of 2 1/2 - 3 inches tall, if that. You're not going to get any shorter than that, even with a wrong-band antenna.

MT2000 man · Post by **MT2000 man** » Wed Oct 22, 2008 4:34 pm

As others have said, don't ruin your radio by using the wrong antenna. Get an OEM Stubby , it's short, and there you go.

res6cue · Post by **res6cue** » Wed Oct 22, 2008 4:58 pm

The question is, what exact min/max frequency range are you transmitting on here? 450-470? 470-512? 800? I've heard people use the term "UHF Hi" to refer to any one of those ranges, so it's not as dumb a question as it sounds to ask you for the specific frequencies you're talking about.

Laird has Tuf Duck stubbies available to cover the entire UHF range. All are under 3" and retail for around $15 each or thereabouts. No reason you shouldn't be able to find one that covers the range you need, instead of taking chances with whatever you're planning on doing with adapters and ham stuff.

EXD-450-SF = 450-470 SMA

EXD-470-SF = 470-512 SMA

EXS-806-SF = 806-866 SMA

Incidentally, you will sacrifice range/performance with these stubbies, so make sure you understand the full impact and implications of switching antennas. Also remember that these stubbies are not at all flexible like the whips are, so if you're wearing the radio on your belt, it might still be poking you in the side, only harder this time.

motorola_otaku · Post by **motorola_otaku** » Wed Oct 22, 2008 5:40 pm

motorola_otaku wrote:
escomm wrote:OEM UHF stubby antennas are about $20
..and are all of 2 1/2 - 3 inches tall, if that. You're not going to get any shorter than that, even with a wrong-band antenna.

I just measured one. 3 3/16, or 8.2 cm.

Post by **akardam** » Wed Oct 22, 2008 6:26 pm

NAE6547AR, 438-470MHz
NAE6548AR, 470-520MHz

Both list at $16.50. At this price, might as well go OEM.

Post by Pj » Wed Oct 22, 2008 6:30 pm

The UHF and up stubby's tend to do the full radio range (with reduced coverage of course).

VHF ones, are very specific (and really are not all that stubby anyways). Even on RX, they drop off like a rock.

(Proud user of the full size VHF and 800 dipole). Large, but they don't poke you like the stubby's do.

Besides, you are already using a full size radio, so whats the extra 2 inches.

Now, if you were using a saber with the long battery - that would look really odd. (Been there, done that, went back to the whip)

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