Can a CB whip antennae work with a Baofeng BF-F8HP?

[WRVM506]

Just curious if this is even a possibility.  I have a project that this setup would work ideally for me but don't want to pursue something that won't work or worse damage the radio.

Thanks,

Dave

[JoCoBrian]

CB:  27 million hertz...give or take.  CB is HF, or high frequency radio

GMRS: 462 million hertz to 467 million hertz  give or take. GMRS is UHF, or Ultra High Frequency Radio. 

By the time you chopped up a CB antenna, and potentially rewind the loading coil, you'd be better off spending $30 on a GMRS antenna. 

A 50 ohm resistor will give you perfect SWR across the bands....but it won't radiate very well. 

[SteveShannon]

Just now, WRVM506 said:

Just curious if this is even a possibility.  I have a project that this setup would work ideally for me but don't want to pursue something that won't work or worse damage the radio.

Thanks,

Dave

Are you able to analyze and trim the whip to the right length?

[WRVM506]

No, I don't have the necessary tools to analyze and trim unless an SWR meter would work.  What should be the right length?  The coax cable is okay to use, right?  Sorry, but I'm still new to GMRS and learning the ropes.  Thanks for your reply.

[WRVM506]

I've used the SWR for tuning cb's and know that the correct setting would be as close to 1.1 : 1 as possible.  Is this the same for GMRS?

[WRWE456]

Welcome! That radio is a ham radio not a GMRS and of course the antenna is not right either. That is kind of a hard way to start in GMRS. Much easier to buy a dedicated GMRS radio and antenna. Can get both for under $100.

What you are asking can be done but there is a learning curve.

[WRVM506]

Thanks for the reply.  I already have a dedicated radio (Midland MXT 575) mounted in my vehicle.  This is for something else. 

I have a WWII Jeep with the 9 section antennae mounted with the period correct mount and base.  I had a hidden CB in the Jeep with a t-17 lollipop mic hooked up to hit.  But now I'd like to use my Baofeng instead and just wondered if I had the right connector would it work with that antennae?

[SteveShannon]

1 hour ago, WRVM506 said:

I've used the SWR for tuning cb's and know that the correct setting would be as close to 1.1 : 1 as possible.  Is this the same for GMRS?

The perfect SWR for any antenna is always 1.0:1, but an SWR up to 2.5 is acceptable if you have low loss feed line. That's true for GMRS as well.

An SWR meter for a CB might not work for the UHF frequencies of GMRS. 

The antenna connectors for CB are usually the same as GMRS, but long lengths of cables that work just fine for CB can really absorb the power of at UHF frequencies, but you probably aren't running more than a few feet in your WWII Jeep. 

As far as whip length, the length of your CB antenna is probably about 103 inches or something like that; that's a quarter wave whip. The wavelength of CB is 11 meters, or around 33 feet. 

The wavelength of GMRS is about 64-65 centimeters or right around two feet, so a quarter wave whip would be around six inches.  That would look pretty tiny compared to the long CB whip.

If I were you, I would just hook up to the antenna and test it to see how it works.  Run at low power at first. Modern radios are amazingly resilient to damage from high SWR.  See if anyone can hear you.

Or stay disconnected from the steel whip and just run your radio with a stubby little GMRS antenna hidden on the Jeep somewhere.

[WRVM506]

Awesome information.  Exactly what I was looking for.  Thanks very much.

[PA141]

Just because an antenna provides a good match does not imply that it will provide any performance off of the design frequency.  Feeding an antenna designed for another frequency may radiate at high angles that are typically not useful and may have a null on the horizon where you typically want your signal to be.  On the other hand, it could have significant gain.  No way to know without modeling it or on air testing.

You can certainly try it and compare to an antenna specifically designed for the frequency.  If it has a reasonable match and outperforms your reference antenna, you have made an improvement.

[WRXP381]

32 minutes ago, JoCoBrian said:

CB:  27 million hertz...give or take.  CB is HF, or high frequency radio

GMRS: 462 million hertz to 467 million hertz  give or take. GMRS is UHF, or Ultra High Frequency Radio. 

By the time you chopped up a CB antenna, and potentially rewind the loading coil, you'd be better off spending $30 on a GMRS antenna. 

A 50 ohm resistor will give you perfect SWR across the bands....but it won't radiate very well. 

This is the correct answer.  The bottom line is not it will not work well if at all. 

[WRKC935]

Well, NO

 

[JoCoBrian]

On 8/29/2024 at 6:00 PM, WRVM506 said:

I've used the SWR for tuning cb's and know that the correct setting would be as close to 1.1 : 1 as possible.  Is this the same for GMRS?

I doubt the CB SWR meter you have will work correctly at UHF frequencies.  There is a HUGE HUGE difference between 27 Mhz and 462 Mhz. 

You could make a simple ground plane antenna out of coat hanger wire, some coax and a couple connectors. 

Or make a J-Pole...

 

[WRVM506]

Thanks for all the replies.

It's not a question of making a GMRS antenna out of a CB antenna FOR MY APPLICATION.  Yes, I could easily purchase a proper antenna.  The reason I'm even asking this question is because I have a WWII Jeep with an antenna that would be originally used with a BC1000 pack radio that TX 40 - 45 MHz.  The antenna is 10'8" long.  I'd like to use the Baofeng hidden inside a radio case that I purchased that has it's guts removed (someone else, not me).  Ergo, the radio would appear to work but using a GMRS radio inside.

Thanks,

Dave

[WRXB215]

@WRVM506 that is very interesting. Maybe you should leave the big antenna as is for looks and add a small, inconspicuous GMRS antenna that actually connects to the radio. A "ghost" antenna might fit the bill.

[Tip10]

Maybe look at making your own j-pole and attaching it to the existing antenna??
Saw an article a while back where some guy made one out of 14 gauge wire — maybe just use heat shrink tubing to attach to big antenna?
Not quite historically accurate but close enough?

Never engage in a battle of wits with an unarmed person.

[WRKC935]

10 hours ago, WRVM506 said:

Thanks for all the replies.

It's not a question of making a GMRS antenna out of a CB antenna FOR MY APPLICATION.  Yes, I could easily purchase a proper antenna.  The reason I'm even asking this question is because I have a WWII Jeep with an antenna that would be originally used with a BC1000 pack radio that TX 40 - 45 MHz.  The antenna is 10'8" long.  I'd like to use the Baofeng hidden inside a radio case that I purchased that has it's guts removed (someone else, not me).  Ergo, the radio would appear to work but using a GMRS radio inside.

Thanks,

Dave

Wish you would have lead with that. 

So what you are asking is sort of possible, but will require some work and performance is NOT going to be what you would expect from a proper antenna.

At the end of the day the radio want's to see a 50 ohm impedance at the antenna port.  Easiest way to get there is an antenna designed for that frequency.  If you don't have that option, then you work with what you have. 

A perfect antenna will present a non-reactive, non-capacitive pure 50 ohm impedance.  But few antenna's are 'perfect'.

So what you end up with too much capacitance or inductance in the presented load.  Which can be countered with addition of the other.  Meaning if the load is inductive, you add capacitance, and vice versa to get the presented load back to 50 ohms.  Problem is the more you add, the narrower the bandwidth.  With an antenna that long, it's going to probably be inductive, so you would need to add capacitance in series of the feed to bring it down.  But that would need to be worked out with an antenna tester that will show you what you need to do. 

Point is that it's not an impossible task, but you are going to need to get your hands on an antenna tester, not just an SWR meter to get it figured out and do some research on antenna design to figure out what you need to do to correct the feed point impedance.

 

[AdmiralCochrane]

The only perfect antenna is a dummy load, but the erp is very low.