[Icom] Greetings - AH4 question

Sat, 21 Sep 2002 14:57:58 -0400

I have obviously got a lot of reading to do.
So far, I am VERY confused!

I don't know how to tell the IC746 to tell the Ah4 TO TUNE!

I will keep reading that site.

Still trying to figure out whether I can use it like this or not!

On 21 Sep 2002 at 11:42, Adam Farson wrote:

> Hi Brian,
> 
> Firstly,  the transceiver's internal autotuner must always be
> disengaged when driving an external tuner. Cascading tuners can
> reflect high reactance values back into the auto-tuner and/or LPF. As
> a result, dangerously high RF voltages can appear across capacitors in
> these networks, leading to component failure.
> 
> If the AH-4 is presenting a grossly mismatched load to the IC-746,
> there may be a fault in the AH-4, or the AH-4 is unable to tune the
> antenna connected to it. A random-length antenna connected to that
> type of coupler may not be a half-wave at any operating frequency.
> 
> The AH-4, AH-3, AT-120 and similar couplers key the transceiver via a
> line which causes the transceiver to put out a 10W tuning signal. As
> far as I recall, the tuner will not dynamically retune if load
> impedance changes whilst transmitting (I may be wrong on this). The
> AH-4 will not tune if the RF input power is less than 5W.
> 
> Here is a website which may be helpful:
> 
> http://www.hamoperator.com/ah4/ah4.htm
> 
> Best 73,
> Adam, VA7OJ/AB4OJ
> North Vancouver, BC, Canada
> http://www.qsl.net/ab4oj/
> Note new e-mail address:
> mailto:[email protected]
> 
> 
> -----Original Message-----
> From: [email protected] [mailto:[email protected]]On
> Behalf Of Brian Carling Sent: Saturday, September 21, 2002 11:11 To:
> [email protected] Subject: [Icom] Greetings - AH4 question
> 
> 
> Hello Icom-ites!
> 
> I am new to the list here, and have a question.
> 
> I had read some of the reviews on eHam.net where they talked about
> using the AH4 tuner.
> 
> A few of the guys use them with the IC-746.
> 
> I have an IC-746 here, and got the two working together, but I have a
> lot of questions.
> 
> The tuner inside the IC746 retunes every time you change bands and
> takes several seconds at full power.
> 
> Does the AH4 ever get to do its "350 mW tuning?"
> 
> Also, I notice that the SWR  back to the 746 appears to usually be
> about 5:1 or at best 3:1 on 30m as shown on the SWR bridge in my
> MFJ-949D.
> 
> Now the 746 always manages to tune out that SWR, but am I losing power
> anywhere with such an arrangement?
> 
> I have more questions but will see what comments and responses this
> brings.
> 
> Thanks everyone.
> 
> Brian ,AF4K
> 
> 
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