[Boatanchors] A question

[Chris Bower]

THAT'S the explanation I was looking for! Thank you, Chuck! Now I understand
what you folks are talking about!

I couldn't care less (at least at this time) about the physical torque load
during tuning. I'm not a young man by any means, but I am an automotive
technician by trade and have been for over 25 years. There ain't a whole lot
on my body that works right anymore, but my hands do. Years of using them to
the point of abuse have built up some very nice muscles in my wrists and
fingers. This is NOT a problem. The creaks and groans of my knees in the
morning are a problem, but working with my hands is not ;-)

You also brought up another good point...when it breaks (which it eventually
will), who is going to work on it? Well, that's why at this time in my "boat
anchor" education, I want a unit that is nearly perfect. If I don't know how
it acts when it's working correctly, how will I know what to look for when
it's broken? With very few exceptions, if you don't know when it's right,
you're going to have a helluva time fixing it when it's broke. As a side
note, I've been telling my customers for years that the cheapest mechanic is
NOT the person you want working on your car. I've found that this idea
follows through to a lot of things in life.

Thanks for your comments and I will be on the lookout for a copy of
"Elements of Radio Servicing". I'll start fixing them up when I completely
understand how they work. Oh, heck, who am I kidding? I'll probably break a
few in the process ;-) 

As Always,
Chris
W1CMB
cmbower@cox.net

P.S. Before I forget, it is the season....Happy Holidays to all and may your
filaments glow brightly throughout the coming year! 



-----Original Message-----
From: Chuck McGregor [mailto:cbmcg@comcast.net] 
Sent: December 8, 2003 7:54 PM
To: Chris Bower
Subject: Re: [Boatanchors] A question 

Chris -
You ask a good question about band cruising vs. tuning a signal (and 
staying there).

The best radio I've owned to date was an R-648,  the little-known little 
brother to the R-390 family, built for use in Navy patrol aircraft. It was 
a pleasure to hear the way stations cleanly moved thru the mechanical 
filter passband as you tuned.  Intererence rejection was fantastic. It was 
stable, with virtually no noticable drift.. BUT, after cruising the band 
awhile, my wrist became very sore !  (So much so that I sold the 
radio.)   The torque needed to tune this radio was very high, compared to 
others.  This is because these wonderful collins radios tune, not by simply 
rotating the shaft of a variable capacitor, but by moving racks of ferrite 
slugs in and out of coils.  There is a sea of gears and gear driven racks 
behind the tuning knob of a collins radio.  With perfect alignment, and 
lubrication, this torque can be reduced, but for the average radio, in 
average condition its still significant, and a real nuisance for most 
casual shortwave listening.

Lesser radios, that tune with a variable capacitor, tend to show much more 
drift (slow detuning) with temperature and time.  This can be reduced, in 
some cases, by various modifications if absolute rock-hard frequency 
stability is important to you.  It probably will not be, unless you spend 
much of your time listening to single sideband communications.  For precise 
knowledge of your tuned frequency you can add an outboard digital frequency 
display to any boatanchor receiver ( see www.aade.com).

A good communications radio's audio section is designed to provide about 
the same audio passband as a telephone,  roughly 150 to 3000 Hz, for good 
voice intelligibility,  nothing more.  And fidelity no better than a 
typical car radio.  And loudness sufficient for listening right at the 
radio.  Some radios, such as the SP200 Super Pro  or the SX-42 provide much 
better audio systems, with higher power output and better quality 
transformers for generally better performance when playing music or 
broadcast program material. Such radios, of course, rarely have a built-in 
speaker, but use an outboard speaker both for fidelity and to prevent 
acoustic feedback from the speaker to the tubes.  Some writers have 
mentioned the alternative, capturing the SP600 audio output from a terminal 
available on the rear of the receiver, and feeding it to an outboard audio 
amplifier.  The same can be achieved with a minor modification to most 
other radios.

One final comment: if you have the misfortune to buy your radio at ebay 
prices, you indeed have a significant investment to worry about when you 
consider who you are going to trust to work on it.  On the other hand, if 
you have the patience and look around a bit you can find some quite good 
radios, needing a little work, really cheap  and learn a lot as you work on 
them. ( I got my SX-42 for $40 and my SP200 for $15 without power 
supply).  You will find the guys on the boatanchors reflectors very 
helpful, although it may be helpful to also have some local help (join the 
nearest ham club).  A good soldering iron and a volt-ohmeter (digital or 
analog) are the only special tools you really have to have.  You may want 
to watch for a copy of "Elements of Radio Servicing" by Marcus and Levy - 
which will explain almost everything you may want to know about the guts of 
a tube radio.

Anyway - I hope these comments are of some use to you.

73 & season's greetings

Chuck  N7RHU