Hypothetical question of UHF antenna bandwidth.

[Elkhunter521]

If someone with a ham license and a UHF radio, were to program the radio to include GMRS frequencies how would you resolve the possible 27 MHz. difference to tune the antenna?

(440 MHz to 467 MHz.) Understanding it would violate FCC regulations to do so?

[Hans]

If someone with a ham license and a UHF radio, were to program the radio to include GMRS frequencies how would you resolve the possible 27 MHz. difference to tune the antenna?

(440 MHz to 467 MHz.) Understanding it would violate FCC regulations to do so?

You're probably already aware, but hams use the same dual band antennas all the time for 2m, MURS, 70cm and GMRS. Along the same lines that berkinet posted, when they want one primarily for 70cm, they buy or make one centered more towards that band. Likewise if they want to primarily use GMRS.

 

*** To those reading... I am not advocating violation of FCC rules on this forum. It is an observation of what has been commonly practiced in my area. That does not make it legally correct. Radio type acceptance must match the service being used to be legal. ***

[Elkhunter521]

If this topic violates any rules or is close, feel free to move it to the private forum.

[berkinet]

Ignoring issues of regulatory compliance, and assuming equal use of both services, you would tune for the center of the band range you wished to broadcast on. Otherwise, if you wanted mostly, say, GMRS, you would bias the “center point” upwards a bit.

 

The actual difference between 420 and 467 is only 47mHz, 1/2 that is roughly 25mHz, or around 5%. Easily within the range of most UHF antenna designs. Obviously, the SWR will rise at the ends of the band range, but should still be quite usable.

[Elkhunter521]

Love this about this web site. You and i are grumping at each other on a different segment yet talking on an other

[berkinet]

Love this about this web site. You and i are grumping at each other on a different segment yet talking on an other

Well, I wasn't really grumping at you... but I have a (excuse the expression) hair trigger on gun issues. (To be clear, I am most definitely not a member of the NRA).

[WRAF213]

The whole range can be covered in a 2:1 VSWR by a dipole or discone pretty easily, but bandwidth is one common trade-off from gain.

[Elkhunter521]

The GUN issue, has no relevance in this Forum. Yes, I am a 2nd amendment advocate but other than FREEDOM I AGREE with you that you are free to express your views in any way you choose.

 

I eas inquiring in reference to your. Superior experience in technology.

[berkinet]

The GUN issue, has no relevance in this Forum. ...

...I was inquiring in reference to your. Superior experience in technology.

 

I guess that was my point as well. This is a radio communications forum with an emphasis on GMRS. I realize that this interest tends to have a lot of crossover with other non-radio interests. And, while I am probably in the minority here on many of those topics, the simple matter is, regardless of where one falls on those issues, they really don't belong here.  As long as we keep to that. any differences should be irrelevant.

 

As to my "superior" experience. Well, I may have a lot of experience, but that does not necessarily equate to knowledge or expertise.  There are others on this forum with a much better technical grounding than me. Probably the one important thing I have learned is to keep my contributions limited to what I know and keep my mouth shut about the rest. That, and I always double check by re-reading my posts, before clicking Post, and by looking up information to be sure I have it right before sharing it with others.  In any case, I sent you a PM earlier and if there is some topic you think would be best handled outside of the forums, feel free to respond.

[Elkhunter521]

Hi berkinet, i have tried this message thing on this forum. Im stupid or my tablet is mad at me today.
Try me at  ---------------------

 

 

 

***Staff Edit - to prevent email spam. (Please use PM to transfer email data,)

[berkinet]

Hi berkinet, i have tried this message thing on this forum. Im stupid or my tablet is mad at me today.

Probably best not to post email addresses in the forum... likely to become spam bait. But, I now have yours and will send an email.

To PM (if you are using a browser in a desktop it tablet) is to click my name in the gray bar above this post, and then click “Send me a Message”

[Elkhunter521]

Wow, i just got popular, mr. Berkinet, try again, i went into delete mode and ........well,sorry

[RCM]

If someone with a ham license and a UHF radio, were to program the radio to include GMRS frequencies how would you resolve the possible 27 MHz. difference to tune the antenna?

(440 MHz to 467 MHz.) Understanding it would violate FCC regulations to do so?

It's not difficult to find an antenna that covers 440-470 with a reasonable swr. I just got a dual band base vhf/uhf antenna that is a half wave on 2M and collinear 5/8 waves on uhf, that covers 440-470 at well under 2:1 swr.

 

And btw, it doesn't necessarily violate FCC regs to have a rig that covers 70cm and GMRS. It can't be frequency agile, but there are no rules I am aware of that prohibit programming ham radio frequencies into a radio that meets type classification for GMRS.

 

Of course, that doesn't mean you can do the MARS/CAP mod on your FT-857 and use it on GMRS!

[russwbrill]

I would use a second antenna dedicated to GMRS..

 

The "All-in-One" antennas are poor performers, most have Zero Gain on any band they operate on..

[Jones]

The whole range can be covered in a 2:1 VSWR by a dipole or discone pretty easily, but bandwidth is one common trade-off from gain.

 

As WRAF213 said earlier, bandwidth is one of the trade-offs from gain.  The higher the gain of the antenna, the narrower its pass-band will be.

 

For best bandwidth, use a 1/4 wave (unity gain) antenna, which will have virtually flat SWR over the entire bandwidth from 430-470MHz.  -OR-

 

For BEST, and most legal results, use separate antennas, AND separate radios for 70cm ham and GMRS services.

 

Also said above, but worthy of repeating: You can legally program a GMRS compliant transceiver such as a Kenwood or Motorola Part 90/95 type-accepted radio to use on ham bands, and still be used on GMRS provided no internal modifications are required that would void type-acceptance... however you are NOT permitted to modify a ham transceiver to transmit on GMRS.