HF Test Set revisited


KD4OBQ
 

Been doing some spring cleaning and came across the HF Test Set and just had to take a break
and play with it for awhile. I forgot how well it works and been having fun getting reacquainted
with it. Everything is working as I remembered and had to play with the TDR of course and forgot
how drifty it was but does get the job done. Looks like I need to pop the hood and see what I put
the 2 momentary switches on to do as they are not identified.

Any one else have one sitting around collecting dust? I am considering passing it on at one point
as it was a fun project and really just use it anymore for testing crystals but actually haven't messed
with any crystals in quite some time.

So if you have one collecting dust consider getting it out and get reacquainted and have some fun.
We are getting more new hams in the area and think I will carry this to the next ham club meeting
and do a demonstration for the new hams and who know it might go home with one of them.

It sure was a fun project and a lot of joy was had by many of us here.

I will post some pictures on my QRZ page of it.

72
Pat KD4OBQ


Tom Sevart
 

On 4/14/2022 22:23, KD4OBQ wrote:
Been doing some spring cleaning and came across the HF Test Set and just had to take a break
and play with it for awhile. I forgot how well it works and been having fun getting reacquainted
with it. Everything is working as I remembered and had to play with the TDR of course and forgot
how drifty it was but does get the job done. Looks like I need to pop the hood and see what I put
the 2 momentary switches on to do as they are not identified.
Any one else have one sitting around collecting dust? I am considering passing it on at one point
as it was a fun project and really just use it anymore for testing crystals but actually haven't messed
with any crystals in quite some time.
So if you have one collecting dust consider getting it out and get reacquainted and have some fun.
We are getting more new hams in the area and think I will carry this to the next ham club meeting
and do a demonstration for the new hams and who know it might go home with one of them.
It sure was a fun project and a lot of joy was had by many of us here.
I will post some pictures on my QRZ page of it.

I use my test set a lot to check crystals. I built mine into an enclosure with a slanted front face, and rather than use jumpers to access each feature, I instead installed a rotary switch to make it a lot more user friendly.

About the only part of it I haven't used is the TDR, since I don't have an O-scope to connect it to.

--
Tom Sevart N2UHC
St. Paul, KS

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nm0s_qrp
 

The new 4SQRP HF Test Set will have a TDR function that will read out directly on an LCD display the location of the fault in nanoseconds from the unit.  You can use that, plus the velocity factor of the cable to locate the fault.  Look for a mid-summer introduction.


Jim Sheldon
 

That will be a great addition to the test equipment line!

For those who do not know what a "TDR" is, TDR stands for Time Domain Reflectometer.  They act as sort of a closed circuit radar for mainly RF cables but they will work on things like network cables and others when some of the basic cable parameters are known.  As long as the cable has continuity, the signal from the TDR will travel down it at a known speed and be reflected back from any impedance changes in that cable.  The velocity factor of the cable must be known to accurately determine just how far the signal propagated down the cable before being reflected back and received at the test set where internal computation determines the distance (usually in feet or meters) between the cable connection on the test set and the fault in the cable that caused the difference in impedance.  This might be a break, a termination on the other end or even a kink or other change in the cable's route and the distance from the test set to the fault (or perceived fault) will allow you to get out your tape measure,  follow the cable to that point and (if buried) dig it up to find and fix that fault.    

Very handy device to have around when needed.

My first encounter with a TDR was back in 1967 when I was stationed in Turkey with the US Army Security agency.  We had a huge problem with the Turkish farmers digging up our buried coax (usually RG-17, 1" or larger hard line and other cables) for the copper they contained.  This would occur mainly at night and created a huge problem for us as they would cover up the dig to the point where it was hard to find.  The TDR (a Hewlett-Packard 140A oscilloscope with a TDR plug-in) allowed us to pinpoint the break, usually within 6 inches to a foot over half a mile or so.  Our people finally got smart and when they replaced the cables, they started covering the cable trench in concrete to prevent such thievery.  Saved us a lot of time, trouble & money by doing that.  

Jim, W0EB

------ Original Message ------
From: "nm0s_qrp" <nm0s@...>
Sent: 4/18/2022 9:02:19 AM
Subject: Re: [4SQRP] HF Test Set revisited

The new 4SQRP HF Test Set will have a TDR function that will read out directly on an LCD display the location of the fault in nanoseconds from the unit.  You can use that, plus the velocity factor of the cable to locate the fault.  Look for a mid-summer introduction.


Curt
 

Glad to hear it's in development in the secret 4S lab operated by the transmitter geek. I had suggested it be revived, and that the Elsie function be integrated to measure inductors and capacitors. I still use the original, in fact I sorted some crystals that I have shared. Oh I think I may have suggested adding the dual signal level function of the former normal generator, that I think is close to S9 and S3. Providing useful tool set encourages home construction. 

73 Curt