Testing, my ART-13, I can obtain a good match on 7 MHz, 10 MHz and 14 MHz, with
the antenna switch (control C) on position 11 or 12.

But when I try to operate on 3.5 MHz, I am unable to obtain a good match at any
antenna switch position. I can get roughly half the RF power with a higher plate
current, this indicating that match is poor. Grid current is OK.

At switch position 8 and above the matching network is a Pi; at position 7 and
below it becomes a simple L.

I know that the transmitter was designed to match short (capacitive) antennas,
and it may then not like the 50-ohm resistance of my 80-meter dipole. But before
carrying out further investigations, I would like to hear if somebody had
experience in operating the ART-13 on 80 meters.

Thanks & 73

Tony I0JX
Rome, Italy

P.S. I do not succeed to get enough grid current at 18.070 MHz that is at the
very extreme of the transmitter operating band

"Antonio Vernucci" wrote in message
...
Testing, my ART-13, I can obtain a good match on 7 MHz, 10
MHz and 14 MHz, with the antenna switch (control C) on
position 11 or 12.

But when I try to operate on 3.5 MHz, I am unable to
obtain a good match at any antenna switch position. I can
get roughly half the RF power with a higher plate current,
this indicating that match is poor. Grid current is OK.

At switch position 8 and above the matching network is a
Pi; at position 7 and below it becomes a simple L.

I know that the transmitter was designed to match short
(capacitive) antennas, and it may then not like the 50-ohm
resistance of my 80-meter dipole. But before carrying out
further investigations, I would like to hear if somebody
had experience in operating the ART-13 on 80 meters.

Thanks & 73

Tony I0JX
Rome, Italy

P.S. I do not succeed to get enough grid current at 18.070
MHz that is at the very extreme of the transmitter
operating band
Are you testing into a dummy load?
If you have an antenna impedance bridge you may be able
to measure the effective impedance of the output stage. If
the transmitter is operating normally you may need some sort
of external tuner.
--
Richard Knoppow
Los Angeles
WB6KBL

Are you testing into a dummy load?

yes, 50 ohm

If you have an antenna impedance bridge you may be able to measure the
effective impedance of the output stage. If the transmitter is operating
normally you may need some sort of external tuner.

I like to operate boatanchors in the way there were supposed to operate. So, if
the ART-13 was not designed to operate on the 80 / 75 MHz band with a 50-ohm
load, I'll just give up.

What I would like to know is whether all the ART-13s behave that way, or I
should instead suspect that a problem occurs on my particular ART-13.

So, I am looking for somebody who can readily fire-up an ART-13 and confirm or
deny my experience.

73

Tony I0JX

On 07/25/2010 06:10 PM, Antonio Vernucci wrote:
Are you testing into a dummy load?

yes, 50 ohm

If you have an antenna impedance bridge you may be able to measure the
effective impedance of the output stage. If the transmitter is
operating normally you may need some sort of external tuner.

I like to operate boatanchors in the way there were supposed to operate.
So, if the ART-13 was not designed to operate on the 80 / 75 MHz band
with a 50-ohm load, I'll just give up.

What I would like to know is whether all the ART-13s behave that way, or
I should instead suspect that a problem occurs on my particular ART-13.

So, I am looking for somebody who can readily fire-up an ART-13 and
confirm or deny my experience.

73

Tony I0JX

In the CQ surplus conversion manual, the one of the chapters on the
ART13 refers to using a 118' flat top antenna feed with a single wire
feeded 17' off center (windom?). The author claims on 80 it acts as a
singe wire feed matched impedance half wave. On 40 and 20 it is a large
T type Marconi. So someone got the rig on 80, but using an old style
wire antenna. I suspect using a modem coax fed antenna with this rig on
80 may be a problem.

Also note that art13's can't normally reach 10 meters, but they have
been converted to this in several ways. One way was to install and
extra multiplier stage where the optional low frequency unit would have
been installed. An extra 10 meter tank coil for the 813 is also added.
Operation on the lower bands is not affected.

There is something to be said for leaving the rig as it was in the
airplane, but I suspect most hams modified these radios somewhat to make
them more useful for civilian use.

Check on the ARRL website and search the QST back issue index for
articles from the late 40's through early '60s and you should find some
articles on the ART13.

Le 26/07/2010 00:27, Kenneth Scharf a écrit :
...
Check on the ARRL website and search the QST back issue index for
articles from the late 40's through early '60s and you should find some
articles on the ART13.

Hi folks, Antonio,

you can download the three volumes of the Surplus Conversion Manuals he

http://www.mines.uidaho.edu/~glowbugs/SurpConv.html


Hope this helps,


Thierry

Kenneth & Thierry

thanks for your answers.

I have found many articles on the web (including the Surplus Conversion
Manuals), but nowhere I found a clear statement that the ART-13 cannot work on
80 meters with a 50-ohm antenna (and that a modification is therefore
necessary).

At present, my main concern is to ascertain whether my particular ART-13 has got
a problem (I hate to have radios that are not perfectly functional), or instead
all ART-13s do not work on 80 meters - by their design - with a 50-ohm antenna.

In the second case, I will just give it up and use - on 80 meters - one of the
many other AM radios I have.

Same conclusion for 10 meters (I have seen that complex modification, but it may
perhaps be worthwhile for those having just a single radio).

73

Tony I0JX

"Thierry_S" ha scritto nel messaggio
r...
Le 26/07/2010 00:27, Kenneth Scharf a écrit :
...
Check on the ARRL website and search the QST back issue index for
articles from the late 40's through early '60s and you should find some
articles on the ART13.

Hi folks, Antonio,

you can download the three volumes of the Surplus Conversion Manuals he

http://www.mines.uidaho.edu/~glowbugs/SurpConv.html


Hope this helps,


Thierry