Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

donate to eham
   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: AH-2B  (Read 2347 times)
HAMIL
Member

Posts: 8




Ignore
« on: June 15, 2003, 08:35:09 PM »

I recently purchased an IC-718 and started looking at antennas.Why do HRO and others want $350 for the AH-2B, a whip? An AH-4 tuner is $259 and Icom says they need to go together. Can I match an MFJ tuner and my own homemade whip to it? I just passed my Tech Test today so Im a newbie but had lots of experience w/ CB as we had a trucking biz.Thanks Karl Hamilton
Logged
KA5S
Member

Posts: 229




Ignore
« Reply #1 on: June 15, 2003, 10:51:26 PM »


No. You do not need to use the Icom whip. They want that kind of money because people who need (or think they need) it will pay that price. But in fact you rarely need it.  It's a good whip, understand. It has an excellent, high-voltage base, and is exceptionally rugged. It's just _expensive_.

I have loaded a 9 foot CB whip (on a _good_ ball-mount) with an AH-2 tuner. The only problem I ever had was when I tried to load the a Hustler with 80 meter coil on 40, using the 5 feet below the coil for the 40 enter antenna, basically, the voltage was high enough that the insulator caught fire.  To be fair, it had a crack in it already, and had road dirt on it. But that's a very short antenna for 40 meters.

On 30 meters and higher frequencies, I found a 9 foot whip worked well enough to only need center loading on 40, 80 and 160.


Cortland
Logged
N8EMR
Member

Posts: 248




Ignore
« Reply #2 on: June 16, 2003, 08:15:27 AM »

The ah-2b is just a CB whip on a big ugly mount. Save yourself a lot of money and get a stainless steel CB whip and a GOOD (NOT FROM RADIO SHACK) antenna mount.
A good hustler mount will do.

Feed it from a Ah4 tuner and off you go.


Neither the ah2b or the CB whip will tune worth a darn on 80m and 40m is a little better but not the best.
The rest of the bands are fine.
Logged
K0BG
Member

Posts: 10248


WWW

Ignore
« Reply #3 on: June 16, 2003, 09:36:46 AM »

As the other folks told you, you do not need the AH-2. The AH-4 autotuner will indeed match an 8.6 foot CB whip on 40, albeit a little lossy. From 20 thru 6 you won't notice much difference between the whip and a center loaded antenna. On some bands and frequencies the whip is better, and on some others the center loaded antenna is better.

You have to watch using just any old antenna and the AH-4 autotuner to work other bands. The Hustler mentioned above is an example of what you can't use! The coil has enough distributed capacitance to make the coil very lossy at bands above its resonant point, and on bands below its resonant point (with the AH-4 retuning it as it were) the voltage is high enough to destroy the coil.

I use an AH-4 and a 20 meter resonant, 13 foot long, antenna which has a coil with low distributed capacitance. It works well from 20 through 6 and is as good as any other antenna on 40. It'll load 80 too, but it is not on par with a good center loaded antenna.

If you decide to use the AH-4 autotuner with a whip, use a VERY GOOD mount with good high voltage isolation or your mount will go up like the above mentioned Hustler coil!

If you want more information on the AH-4 here is a place to go:

http://www.hamoperator.com/ah4/

Alan, KØBG
Logged

HAMIL
Member

Posts: 8




Ignore
« Reply #4 on: June 16, 2003, 10:16:49 AM »

Ok, Thanks everyone. A guy I know said to use extra phenolic insulation , raising it at the bottom away from the mount to prevent arcing and go for it too. Karl
Logged
K0BG
Member

Posts: 10248


WWW

Ignore
« Reply #5 on: June 16, 2003, 04:41:41 PM »

Well, maybe it will and maybe it won't! If it get damp (not wet, just damp) due to washing the vehicle or rain, you run a good chance it will arc regardless.

The least problematic material is Delron or teflon.


Alan, KØBG
Logged

AA4PB
Member

Posts: 15065




Ignore
« Reply #6 on: June 16, 2003, 08:01:46 PM »

One of the reasons for the expense is the custom "big ugly insulator".  A standard CB type ball mount is marginal for the high voltages likely to be developed at the base of the whip on the lower frequencies when running 100 watts or more. The shorter the whip (in terms of wavelength) the higher the voltage at the base. The longer the connecting wire between the tuner and the base of the whip, the higher the voltage at the insulator. When using a tuner/whip combination you are dealing with a completly different thing than the typical loaded antenna that presents an impedance at the base of somewhere near 50 ohms or less. The impedance at the base of an unloaded, short whip antenna is quite high, therefore the voltage is high.

The little nylon sholder washer type insulators used on mirror, trunk lid and similar type mounts are totally inadaquate for a tuner/whip type installation.

For a worse case scenario I modeled an 8-foot whip with a 1-foot feed wire on 3.5 Mhz. With 100 watts you can expect to see in the neighborhood of 1000 volts across the insulator. I use a stake pocket mount on a pick up and machined my own custom insulator from a 3-inch long, 1.5-inch diameter Delrin rod. This is similar to the insulator that SGC uses on their (also very expensive) whip antenna.

To get some ideas and suggestions about mounts in this type of application, you might want to take a look at some of the info and FAQs on the SGC web page http:\\www.sgcworld.com
Logged

Bob  AA4PB
Garrisonville, VA
HAMIL
Member

Posts: 8




Ignore
« Reply #7 on: June 17, 2003, 12:53:22 AM »

Ok thanks, Im still trying to decide how to do this so any help is greatly appreciated. Karl
Logged
K0BG
Member

Posts: 10248


WWW

Ignore
« Reply #8 on: June 18, 2003, 09:48:40 AM »

You might want to read several articles I posted here on eham.net. The URLs are as follows:

http://www.eham.net/articles/4407
http://www.eham.net/articles/4424
http://www.eham.net/articles/4425
http://www.eham.net/articles/4623

Alan, KØBG
Logged

WA5HSV
Member

Posts: 3




Ignore
« Reply #9 on: December 07, 2006, 07:08:25 AM »

I tried a "CB" whip with an AH-4 and it would NOT load on sum bands.  The people I bought the AH-2b from sent a CB whip instead of the right one.  I then got the right one from them and it loaded every where including the MARS freqs.  Good luck.  I think its worth the money.
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!