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Old June 6th 07, 04:21 PM posted to rec.radio.cb
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Posts: 298
Default Modulation on scope question

On Sun, 03 Jun 2007 21:29:09 -0400, Vinnie S.
wrote:

+++I am restoring an old TRC-455, and want to align it by Sams. I have a Tek scope,
+++but a standard 10x probe. Do I need a probe with a certain bandwidth?
+++
+++Vinnie S.

*************

A scope probe with 50 MHz bandwidth will be suficient. The bandwidth
of the probe is stated so that you will avoid attenuation issues at
high frequencies. Measurements above the rated bandwidth of the scope
probe will yield inaccurate measurement levels. If you are just
looking for the presence of a signal and the absolute level is not
needed then don't worry to much about the bandwidth of the scope
probe.

james
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Old June 6th 07, 11:55 PM posted to rec.radio.cb
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Default Modulation on scope question

On Wed, 06 Jun 2007 15:21:49 GMT, james wrote:

On Sun, 03 Jun 2007 21:29:09 -0400, Vinnie S.
wrote:

+++I am restoring an old TRC-455, and want to align it by Sams. I have a Tek scope,
+++but a standard 10x probe. Do I need a probe with a certain bandwidth?
+++
+++Vinnie S.

*************

A scope probe with 50 MHz bandwidth will be suficient. The bandwidth
of the probe is stated so that you will avoid attenuation issues at
high frequencies. Measurements above the rated bandwidth of the scope
probe will yield inaccurate measurement levels. If you are just
looking for the presence of a signal and the absolute level is not
needed then don't worry to much about the bandwidth of the scope
probe.

james



I just wanted to measure modulation on a TRC-455 that I am restoring. I have a
10x probe with the bandwidth being 60Mhz in the 10x position.

But I have bad news. I apparently need and RF generator for alignment of the
receiver. I do not own one. I have everything else. So off to ebay I go. Any
recommendations?

Vinnie S.
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Old June 7th 07, 05:11 AM posted to rec.radio.cb
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Posts: 44
Default Modulation on scope question

Vinnie;

Why don't you just try using another radio as the signal source? Run it in
to a dummy load. A loop or two around the dummy load may pick up enough
signal leakage that you can feed it in to the rig you're setting up.

--
Regards,
Leland C. Scott
KC8LDO

"Vinnie S." wrote in message
...
On Wed, 06 Jun 2007 15:21:49 GMT, james wrote:

On Sun, 03 Jun 2007 21:29:09 -0400, Vinnie S.
wrote:

+++I am restoring an old TRC-455, and want to align it by Sams. I have a
Tek scope,
+++but a standard 10x probe. Do I need a probe with a certain bandwidth?
+++
+++Vinnie S.

*************

A scope probe with 50 MHz bandwidth will be suficient. The bandwidth
of the probe is stated so that you will avoid attenuation issues at
high frequencies. Measurements above the rated bandwidth of the scope
probe will yield inaccurate measurement levels. If you are just
looking for the presence of a signal and the absolute level is not
needed then don't worry to much about the bandwidth of the scope
probe.

james



I just wanted to measure modulation on a TRC-455 that I am restoring. I
have a
10x probe with the bandwidth being 60Mhz in the 10x position.

But I have bad news. I apparently need and RF generator for alignment of
the
receiver. I do not own one. I have everything else. So off to ebay I go.
Any
recommendations?

Vinnie S.



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Old June 7th 07, 10:44 PM posted to rec.radio.cb
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First recorded activity by RadioBanter: Sep 2006
Posts: 298
Default Modulation on scope question

On Wed, 06 Jun 2007 18:55:21 -0400, Vinnie S.
wrote:

+++On Wed, 06 Jun 2007 15:21:49 GMT, james wrote:
+++
+++On Sun, 03 Jun 2007 21:29:09 -0400, Vinnie S.
+++wrote:
+++
++++++I am restoring an old TRC-455, and want to align it by Sams. I have a Tek scope,
++++++but a standard 10x probe. Do I need a probe with a certain bandwidth?
++++++
++++++Vinnie S.
+++*************
+++
+++A scope probe with 50 MHz bandwidth will be suficient. The bandwidth
+++of the probe is stated so that you will avoid attenuation issues at
+++high frequencies. Measurements above the rated bandwidth of the scope
+++probe will yield inaccurate measurement levels. If you are just
+++looking for the presence of a signal and the absolute level is not
+++needed then don't worry to much about the bandwidth of the scope
+++probe.
+++
+++james
+++
+++
+++I just wanted to measure modulation on a TRC-455 that I am restoring. I have a
+++10x probe with the bandwidth being 60Mhz in the 10x position.
+++
+++But I have bad news. I apparently need and RF generator for alignment of the
+++receiver. I do not own one. I have everything else. So off to ebay I go. Any
+++recommendations?
+++
+++Vinnie S.

*****************

I have an HP 8656 generator. A bit pricy even still today. I got mine
at a fantastic price 8 yrs ago. Bought it when the factory was closing
down and moving as excess equiptment for around $400. They are still
commanding around $700 to $1000.

Really for CB work if you can find any of the older B&K CB test
equiptment in decent shape I would suggest those. Equiptment like HP,
Wavetek, and others are very pricy for home test equiptment.

james
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Old June 10th 07, 05:03 PM posted to rec.radio.cb
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Default Modulation on scope question

James;

One of the problems buying used test equipment is the manufacture finds
there is some weakness in the design resulting in frequent failures, one
reason why they may quit manufacturing it.

I don't know if the HP signal generator you mentioned is one such item. I
remember in some back issues of QEX somebody came up with a modification to
replace a section in the output of a HP signal generator that was known to
be particularly failure prone, the original part used isn't available
anymore if I remember right.

Others have picked up old Tech scopes real cheap that had problems, hoping
to fix them, and finding out that the blown parts, like Tunnel Diodes, are
now almost imposable to find since almost nobody makes them anymore. And the
ones that do, if you can find the exact one you need, want such a high price
for them it isn't worth it.
--
Regards,
Leland C. Scott
KC8LDO


"james" wrote in message
...
On Wed, 06 Jun 2007 18:55:21 -0400, Vinnie S.
wrote:

+++On Wed, 06 Jun 2007 15:21:49 GMT, james wrote:
+++
+++On Sun, 03 Jun 2007 21:29:09 -0400, Vinnie S.
+++wrote:
+++
++++++I am restoring an old TRC-455, and want to align it by Sams. I
have a Tek scope,
++++++but a standard 10x probe. Do I need a probe with a certain
bandwidth?
++++++
++++++Vinnie S.
+++*************
+++
+++A scope probe with 50 MHz bandwidth will be suficient. The bandwidth
+++of the probe is stated so that you will avoid attenuation issues at
+++high frequencies. Measurements above the rated bandwidth of the scope
+++probe will yield inaccurate measurement levels. If you are just
+++looking for the presence of a signal and the absolute level is not
+++needed then don't worry to much about the bandwidth of the scope
+++probe.
+++
+++james
+++
+++
+++I just wanted to measure modulation on a TRC-455 that I am restoring. I
have a
+++10x probe with the bandwidth being 60Mhz in the 10x position.
+++
+++But I have bad news. I apparently need and RF generator for alignment
of the
+++receiver. I do not own one. I have everything else. So off to ebay I
go. Any
+++recommendations?
+++
+++Vinnie S.

*****************

I have an HP 8656 generator. A bit pricy even still today. I got mine
at a fantastic price 8 yrs ago. Bought it when the factory was closing
down and moving as excess equiptment for around $400. They are still
commanding around $700 to $1000.

Really for CB work if you can find any of the older B&K CB test
equiptment in decent shape I would suggest those. Equiptment like HP,
Wavetek, and others are very pricy for home test equiptment.

james





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Old June 10th 07, 08:41 PM posted to rec.radio.cb
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Default Modulation on scope question

On Sun, 10 Jun 2007 12:03:04 -0400, "Leland C. Scott"
wrote:

+++James;
+++
+++One of the problems buying used test equipment is the manufacture finds
+++there is some weakness in the design resulting in frequent failures, one
+++reason why they may quit manufacturing it.
+++
+++I don't know if the HP signal generator you mentioned is one such item. I
+++remember in some back issues of QEX somebody came up with a modification to
+++replace a section in the output of a HP signal generator that was known to
+++be particularly failure prone, the original part used isn't available
+++anymore if I remember right.

******************

The HP generator I have is a standard that HP sold for commercial and
industrial use throughout much of the 1990's but now is discontinued.
The one I have is a HP8656A with the attenuator replaced with the
same one that was used in the HP8656B. One of the HP8656A's main
weakness was that of the attentuator at the output. The genreator has
an input for connection to a high stability time base which improves
the performance especially when using it at frequencies around 800
MHz. I also have a 10MHz. high stability TXCO that keeps the accuracy
of the generator frequency set to less than +/- 1 Hz.

Obsolescence is not necessarily due to problem plagued unit though
that can be a cause. WIth HP8656/57 series that may not have been the
problem. Lower demand and cost of manufacturing can also lead to
obsolescence. Lack of demand can be due to not having features and
options that the end user demands. Often a new model is introduced
with more bells and whistles as well as defect fixes that will all but
obsolete the previous model.

I have been very happy with the unit I have. The front keypad is still
in very excellent shape as the unit I have was on the factory floor
and control of it was via the GPIB connection from an HP workstation.

james
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Old June 11th 07, 12:04 AM posted to rec.radio.cb
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Posts: 44
Default Modulation on scope question


"james" wrote in message
...
I have been very happy with the unit I have. The front keypad is still
in very excellent shape as the unit I have was on the factory floor
and control of it was via the GPIB connection from an HP workstation.


Well that's good. I'm a bit leery of spending big bucks on used test gear
since you don't know what the last guy did to it abuse wise, something
stupid like keying up the xmit with the signal generator still attached. I
found that if the equipment looks good cosmetically there is a good chance
the guy selling it didn't abuse the equipment, much.

I would like to get a nice spectrum analyzer but anything worth having is in
the $2K range, a bit too much to take a chance on it from a total stranger.
I could spent $6K on a nice new portable LCD one. 8-))


--
Regards,
Leland C. Scott
KC8LDO



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Old June 12th 07, 03:29 AM posted to rec.radio.cb
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Posts: 298
Default Modulation on scope question

On Sun, 10 Jun 2007 19:04:01 -0400, "Leland C. Scott"
wrote:

+++
+++"james" wrote in message
m...
+++ I have been very happy with the unit I have. The front keypad is still
+++ in very excellent shape as the unit I have was on the factory floor
+++ and control of it was via the GPIB connection from an HP workstation.
+++
+++Well that's good. I'm a bit leery of spending big bucks on used test gear
+++since you don't know what the last guy did to it abuse wise, something
+++stupid like keying up the xmit with the signal generator still attached. I
+++found that if the equipment looks good cosmetically there is a good chance
+++the guy selling it didn't abuse the equipment, much.
+++
+++I would like to get a nice spectrum analyzer but anything worth having is in
+++the $2K range, a bit too much to take a chance on it from a total stranger.
+++I could spent $6K on a nice new portable LCD one. 8-))

*****************

If you want a Spectrum Analyzer just to monitor your transmitter
signals and not do design work with there are a couple of nice
circuits on teh net that can be put together for under $200. Maybe
under $100.

The one by the Green Bay Professional Packet Radio group is a nice one
for signal monitoring. It is based on the W7ZOI and K7TAU circuits and
is a better one as it will work up to 1Gig. Granted these are not as
good as commercial built test equiptment but for monitoring emmisions
compliance it is better than nothing. I think the circuit would be
neat to interface it to a quarter VGA color LCD panel.

james
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