I just built a 1/4 wave (146mhz) antenna for my dual band
HT (Yaesu FT-51r). It's simply 19.25" of .025" piano wire
soldered into the core of a broken SO-239/BNC adapter.
The BNC center pin just sits in the socket in the radio with
a rubber bnc cap keeping the antenna load off the pin and
keeping dirt out. It's all a press fit and it seems to work great.

Comparing it to my OEM rubber duck, it's about 2-4 S units
better on 2m & 440. As I understand it, it works as a 3/4
wave antenna on UHF and should be a good match but the
radiation angle won't be perfect.

My question is this: What would be the radiation angle on 440?

I know I'm picking nits here but I'm interested in the theroy.

P.S. The FT-51R is an all metal case HT which should provide
a good capacitive couple to my hand but what about when
the HT is on the back of my backpack? What counterpoise do
I get then? Maybe from the mic cable?
--
73 de Ken KGØWX - Flying Pigs #-1055
Elecraft K2 #4913

Ken Bessler wrote:
I just built a 1/4 wave (146mhz) antenna for my dual band
HT (Yaesu FT-51r). It's simply 19.25" of .025" piano wire
soldered into the core of a broken SO-239/BNC adapter.
The BNC center pin just sits in the socket in the radio with
a rubber bnc cap keeping the antenna load off the pin and
keeping dirt out. It's all a press fit and it seems to work great.

Comparing it to my OEM rubber duck, it's about 2-4 S units
better on 2m & 440. As I understand it, it works as a 3/4
wave antenna on UHF and should be a good match but the
radiation angle won't be perfect.

My question is this: What would be the radiation angle on 440?

I know I'm picking nits here but I'm interested in the theroy.

P.S. The FT-51R is an all metal case HT which should provide
a good capacitive couple to my hand but what about when
the HT is on the back of my backpack? What counterpoise do
I get then? Maybe from the mic cable?
--
73 de Ken KGØWX - Flying Pigs #-1055
Elecraft K2 #4913


In a HT I would not worry about radiation angle.

Dave WD9BDZ

Ken Bessler wrote:
I just built a 1/4 wave (146mhz) antenna for my dual band
HT (Yaesu FT-51r). It's simply 19.25" of .025" piano wire
soldered into the core of a broken SO-239/BNC adapter.
The BNC center pin just sits in the socket in the radio with
a rubber bnc cap keeping the antenna load off the pin and
keeping dirt out. It's all a press fit and it seems to work great.

Comparing it to my OEM rubber duck, it's about 2-4 S units
better on 2m & 440. As I understand it, it works as a 3/4
wave antenna on UHF and should be a good match but the
radiation angle won't be perfect.

My question is this: What would be the radiation angle on 440?

It's just about impossible to say. Your body is radiating at least as
much as the "antenna", and the pattern is determined the combination.

I know I'm picking nits here but I'm interested in the theroy.

The theory says that if you put any current I into the antenna, an equal
current I flows from the inside of the antenna connector shell over the
edge, over the HT case, and into any conductor it can find. The amount
of radiation from the antenna is proportional to the current on each
part of the antenna multiplied by the length of wire it flows on. The
radiation from the HT case or your body is proportion to the current on
each part of it multiplied by the length of the conductor it flows on.
Your body and the HT case follow the same rules as the "antenna", and
are at least as important a part of the radiating system. The overall
pattern is the sum of the fields from all those current-conductor length
products, from both the "antenna" and your body.


P.S. The FT-51R is an all metal case HT which should provide
a good capacitive couple to my hand but what about when
the HT is on the back of my backpack? What counterpoise do
I get then? Maybe from the mic cable?

Yes, the mic cable and case will become the other half of the antenna
system. If you unplug the mic, the current into the "antenna" will drop
(on 2 meters at least) because the impedance of the outside of the case
will be relatively high because of its short length. And only the amount
of current that flows on the outside of the case will flow into the
"antenna".

Roy Lewallen, W7EL