[ARC5] ARC5 Digest, Vol 86, Issue 41 - Tuning Capacitor removal
Andy Young
andy-young at supanet.com
Sun Mar 20 17:40:01 EDT 2011
Hi Mike,
An interesting approach, but I'm not sure I have the nerve for it!
On the other hand the antenna post survived the force to cause the damage in
the first place.....
It will be next weekend before I get an opportunity to do anything now.
Many thanks,
Andy
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Sent: Sunday, March 20, 2011 6:30 PM
Subject: ARC5 Digest, Vol 86, Issue 41
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> Today's Topics:
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> 1. Re: Tuning Capacitor Removal - Help, please! (Mike Hanz)
> 2. Utility Amp Driving Advice. (David Stinson)
> 3. Re: Utility Amp Driving Advice. (Bob Macklin)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sun, 20 Mar 2011 14:03:09 -0400
> From: Mike Hanz <aaf-radio-1 at aafradio.org>
> Subject: Re: [ARC5] Tuning Capacitor Removal - Help, please!
> To: ARC-5 List <arc5 at mailman.qth.net>
> Message-ID: <4D86415D.9070903 at aafradio.org>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Good advice from Dave and Ken.
>
> On items like this, I always start out with the "equal but opposite"
> ploy, but it assumes you have some method that you can use to give slow,
> graduated pressure to whatever is bent. A good example is in the top
> two photos at http://aafradio.org/garajmahal/BC-AA-191.htm where a steel
> strut needed to be straightened. On the command receivers, the panel
> metal is very soft, as Ken noted, so it does make it a bit easier. One
> technique that you may be able to accomplish is to clamp the receiver on
> the table of a drill press - upside down in your case - using soft
> protection between the receiver and the steel table. Then chuck a long
> 1/2" bolt in the drill chuck. You should then be able to preposition
> the head of the bolt at the tip of the bent down antenna post and begin
> to apply some pressure to it. Then look at the metal surrounding the
> insulator. If there are no ripples being formed in it, then move the
> downfeed lever a bit more. You do risk breaking the ceramic insulator,
> but they are pretty resistant to steady pressure like this...it's impact
> that they don't like. Just take your time and watch the area
> surrounding the insulator for distortion. Once the insulator is
> completely horizontal again, you can make a determination if further
> work is needed to flatten the panel...aluminum is unfortunately a
> "stretchy" metal, so ripples are sometime unavoidable, but I would try
> the slow pressure approach first - you may be fortunate. Another
> approach would be to clamp the receiver on the edge of a workbench and
> do something similar with a large C-clamp. Once you get the antenna
> post straight again, you can decide whether you need to do more, which
> essentially says you will have to remove the capacitor per Dave and
> Ken's advice. If you do have any ripples, then a bolt and nut with a
> couple of washers can be threaded through the insulator hole and used as
> a compression flattener.
>
> Let us know how it goes,
> Mike KC4TOS
>
>
> ------------------------------
>
> Message: 2
> Date: Sun, 20 Mar 2011 13:12:14 -0500
> From: "David Stinson" <arc5 at ix.netcom.com>
> Subject: [ARC5] Utility Amp Driving Advice.
> To: <milsurplus at mailman.qth.net>, "ARC-5 List" <arc5 at mailman.qth.net>
> Message-ID: <39797C49CC824B10BBBD2542503DBB0B at DaddyPC>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> reply-type=original
>
> Many of my light-air radios output under five watts- some less than 2.
> They need a little boost on 75 mtr AM.
> I used a Motorola Triton 40S marine SSB rig as the heart
> of a utility linear amplifier. Works well on the air
> on 160, 80, 40 and 30 mtrs (the rig is speced to 12 MC).
>
> Here's a couple of photos:
>
> http://home.netcom.com/~arc5/amp1.JPG
>
> http://home.netcom.com/~arc5/amp2.JPG
>
> I tapped into the driver input and brought-out
> the receiver antenna lead. The rig is rated at 125 W PEP SSB.
> I cranked it back so that the unmodulated carrier is 40 watts,
> which is serviceable on good days and
> can drive a bigger amp if needed.
> RF envelope at the output while modulating
> looks excellent and reports are good.
>
> The drive level needed for full output
> is just 10 milliwatts into 50-ohms.
> I terminated the RF Input with a 50-ohm, 3 dB pad.
> I'm building a step-attenuator so I can drive it with
> anything from 7 watts (my SCR-288) down to
> sig-gen levels.
>
> I want to protect the input so I don't blow-up the driver.
> If I calculated correctly, 10 milliwatts in 50 ohms should
> be 1.414 Volts PTP. If so, a simple set of four
> "up" and "down" ( or "left-n-right" ;-) silicon diodes-
> each leg with two in series to to ground, which
> will forward bias at 1.4 volts and limit the input
> to 20 milliwatts, should do the trick.
> At lower drive levels, they should be "invisible."
> At high levels, they'll clip and distort.
> And when I screw-up and pop 40 watts into it,
> they should short and save my amp.
>
> First- did I get the math right?
> Second- what blatantly obvious thing am I missing?
>
> Thanks, Dave S. AB5s
>
>
>
> ------------------------------
>
> Message: 3
> Date: Sun, 20 Mar 2011 11:30:42 -0700
> From: Bob Macklin <macklinbob at msn.com>
> Subject: Re: [ARC5] Utility Amp Driving Advice.
> To: "David Stinson" <arc5 at ix.netcom.com>,
> <milsurplus at mailman.qth.net>, "ARC-5 List" <arc5 at mailman.qth.net>
> Message-ID: <BLU0-SMTP15835A9B834AACC0FDE43F0C5B20 at phx.gbl>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> reply-type=original
>
> DX-40s and DX-60s are quite common. Why not modify one of them to operate
> as
> a linear for the small radios.A Dx-60 should give you about 15W of AM
> carrier.
>
> Bob Macklin
> K5MYJ
> Seattle, Wa.
> "Real Radios Glow In The Dark"
>
> ----- Original Message -----
> From: "David Stinson" <arc5 at ix.netcom.com>
> To: <milsurplus at mailman.qth.net>; "ARC-5 List" <arc5 at mailman.qth.net>
> Sent: Sunday, March 20, 2011 11:12 AM
> Subject: [ARC5] Utility Amp Driving Advice.
>
>
>> Many of my light-air radios output under five watts- some less than 2.
>> They need a little boost on 75 mtr AM.
>> I used a Motorola Triton 40S marine SSB rig as the heart
>> of a utility linear amplifier. Works well on the air
>> on 160, 80, 40 and 30 mtrs (the rig is speced to 12 MC).
>>
>> Here's a couple of photos:
>>
>> http://home.netcom.com/~arc5/amp1.JPG
>>
>> http://home.netcom.com/~arc5/amp2.JPG
>>
>> I tapped into the driver input and brought-out
>> the receiver antenna lead. The rig is rated at 125 W PEP SSB.
>> I cranked it back so that the unmodulated carrier is 40 watts,
>> which is serviceable on good days and
>> can drive a bigger amp if needed.
>> RF envelope at the output while modulating
>> looks excellent and reports are good.
>>
>> The drive level needed for full output
>> is just 10 milliwatts into 50-ohms.
>> I terminated the RF Input with a 50-ohm, 3 dB pad.
>> I'm building a step-attenuator so I can drive it with
>> anything from 7 watts (my SCR-288) down to
>> sig-gen levels.
>>
>> I want to protect the input so I don't blow-up the driver.
>> If I calculated correctly, 10 milliwatts in 50 ohms should
>> be 1.414 Volts PTP. If so, a simple set of four
>> "up" and "down" ( or "left-n-right" ;-) silicon diodes-
>> each leg with two in series to to ground, which
>> will forward bias at 1.4 volts and limit the input
>> to 20 milliwatts, should do the trick.
>> At lower drive levels, they should be "invisible."
>> At high levels, they'll clip and distort.
>> And when I screw-up and pop 40 watts into it,
>> they should short and save my amp.
>>
>> First- did I get the math right?
>> Second- what blatantly obvious thing am I missing?
>>
>> Thanks, Dave S. AB5s
>>
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> End of ARC5 Digest, Vol 86, Issue 41
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