5/8 over 1/4 , 800 Mhz, resonant on VHF?

[jparks29]

I've been looking at the 800 Mhz antennas, overall length is 14", but with the coil in the middle, I'm thinking it could easily be 5" or so which would mean an electrical length of about 19", perfect for 2m.

All the VHF disguise antenna's I've installed look identical to the 800 antenna..


Thoughts, Ideas??


Here's a pic of the 800 Mhz with coil...

And the 'disguise' VHF antenna...

 

[zz0468]

That's not how it works... the electrical length of a loaded antenna isn't necessarily the same as the physical length if you stretch out the loading coil.

Beyond that, I'm not sure what you're asking us for...

 

[n2mdk]

That coil isn't a loading coil, it's there for phasing of the 2 elements.

 

[W4KRR]

That's not how it works... the electrical length of a loaded antenna isn't necessarily the same as the physical length if you stretch out the loading coil.
Beyond that, I'm not sure what you're asking us for...

I think he's asking if an 800MHz antenna (the type with the coil) could be used for two meters. I would say no, especially if you intend to use it to transmit on two meters. I would use a dedicated antenna designed for two meters, or whatever band or bands you intend to transmit on.

 

[rankin39]

A fellow on one of the radio lists checked one of those little cellular "pigtails" and found it resonated up around 190 MHz. This is plenty good for just listening around high band, but it wouldn't be good for transmitting. The slightly larger 800 antenna with a half-wave feeding a 5/8 wave would be even better, but maybe still not right for transmitting. Today's solid state transmitter finals aren't very tolerant of high s.w.r.
Bob, w0nxn

 

[zz0468]

That coil isn't a loading coil, it's there for phasing of the 2 elements.

True, that. Semantics...

 

[n2mdk]

True, that. Semantics...

Err no, Physics :lol:

 

[jonny290]

You could clip a small shorting wire between the top and bottom of the coil, negating it, giving you a straight 1/4 wave whip. You might need to add an inch on top, though, and at that point, just find a spring steel or brass rod that'll fit into your base and then cut it for your frequency.

 

[obijohn]

That coil isn't a loading coil, it's there for phasing of the 2 elements.

Then explain why the antenna is resonant at vhf ?

It may act as a phasing section at 800 MHz, but it is acting as a loading coil at vhf.

In my experience, the 800 antenna that is being discussed makes an excellent vhf receive antenna. I listen to a vhf repeater 25 plus miles away using one of these on a scanner in my car.

 

[n2mdk]

Then explain why the antenna is resonant at vhf ?

It may act as a phasing section at 800 MHz, but it is acting as a loading coil at vhf.

In my experience, the 800 antenna that is being discussed makes an excellent vhf receive antenna. I listen to a vhf repeater 25 plus miles away using one of these on a scanner in my car.

What kind of SWR do you get when using it on VHF?

 

[gcgrotz]

I've used cell magmounts for scanning, they work quite well on VHF. Not sure of resonant freq or anything close to resonance at VHF but it will work for most local scanning - don't worry about it if it works.

 

[jparks29]

I'll just buy the 'real' antenna...

It'd be for transmit..

 

[zz0468]

I'll just buy the 'real' antenna...

It'd be for transmit..

I was kinda wondering when someone would come to that conclusion. :roll:

 

[K9JLR]

I'll just buy the 'real' antenna...

It'd be for transmit..

The 800 MHz pigtail antenna is NOT a good choice for transmit on 2 meters..good conclusion..tried it on an antenna analyzer..no go.

However, it is hands down the best all-band receive antenna that I have ever used. I've tried just about every antenna, save for the Austin, and it performs as the best scanner antenna across the major scanning bands (VHF - 800 MHz). It even picked up ISP on lowband failry well.