The Dummyloads

Where ham brains come to fry

Where ham brains come to fry

Rig Expert

My Rig Expert AA-230 Broke!

When I was evaluating who I was going to purchase my Rig Expert from, I spent some time studying up on which vendor I should buy from.  You can get them from DX Engineering, PNC Engineering, Amazon, Giga Parts, etc.  I chose to order from PNC Engineering because of this statement from their website. (italics added for emphasis)

Why Buy From PNC Engineering?

PNC Engineering covers all RigExpert Analyzers under our United States “in-house” warranty center. Out of warranty repairs may also be contracted through PNC Engineering. RigExpert products purchased from other vendors must be serviced in Canada or in the Ukraine where RigExpert Analyzers are manufactured. This will require the customer to pay the shipping costs of their product to one of those out of country locations. With PNC Engineering your shipping expenses are considerably less, and shipping times much faster due to our ‘local’ U.S. location. 

I mentioned in my initial assessment of the analyzer that it had given me infinite readings initially.  Being a newb to this tool, I just assumed that I had neglected to fasten the N to SO-239 adapter correctly.  I finally got it to give me a flat reading on a dummy load and was happy with the measurements.

My friend Myron WV0H mailed me a few N adapters and 50 ohm loads.  No longer would I need to do SO-239 to PL-259 to BNC.  The adapter stack was getting out of control. . . So I connected the N to SMA and an SMA 50 ohm load.  Infinite SWR.  Hmmm. . .  Well, the loads are ham fest deals so maybe its a dud.  Lets try another.

Infinite.

OK. . . lets do a dummy load I know works.  So I do the N to BNC adapter.  Then a short coax jump to my dummy load.

Infinite.

OK. . . lets do a known adapter stack that has worked previously.

Your guess is correct.  Infinite!

Then I started loosening the threads on the N connector and I got an accurate reading.  Hmmm. . . this is not good.

**********Do NOT EVER do what I am about to do***********

I turn off the machine.  I take the adapter stack off and look down into the N connector.  All looks normal.  I then take a screw driver and make contact with the center pin.  It moves!!  It moves a lot and I am not putting any effort into touching it.

******You CAN DO everything below this line safely************

So I fire off an email to PNC Engineering.  They send back a form letter that is intimidating.  I kindly respond with the situation and assure them I’m going to mail this thing back for repair under warranty.  A few pages of paperwork and $20 in mailing and insurance later, the device is in the mail to California.

A few days go by and I get a confirmation they received it.  The next day I get a note that they are going to repair it under warranty and send me a new one.  I am looking forward to it arriving!

So. . . I’m hear to tell you that PNC Engineering is good to their word.  (Although the shipping time is a week)  It’s possible I could have just returned it via Amazon and bought another.  Maybe I’m not getting a great deal since I had to pay shipping.  I really like the device and have LOTS of plans to measure stuff and report back!

KF5RY

My Rig Expert AA-230 Has Arrived

I cannot express to you how excited I am about this thing.  Unfortunately I have a grand total of zero N type connectors or devices that have N type connectors on them.  Fortunately Rig Expert provides an N to SO-239 adapter.  I can get from SO-239 to pretty much anything else I might need.

An example of what you can see with a Rig Expert.

Strangely upon getting this thing I had a heck of a time getting it to give me a legit measurement.  For some reason I kept getting an infinite measurement.  The first thing I wanted to test was my dummy load.  No luck.  Then I decided I wanted to see what the Smith Chart looked like on some conventional Transformers I had built some time ago.  I know that the inductance checked out on the windings, but I had never had a measurement device capable of showing me if it actually worked.  So I found a 200 Ohm resistor to test my 4:1 conventional transformer.  This should give me a reading pretty near 1:1 SWR.

Infinite.

Maybe I got a bad resistor.  After wiggling things a bit and trying a new resistor.  BAM. . . I have a reading.  It checks out.  I go on the the 2:1 transformer, etc.  All tests come out showing that I did in fact make these things correctly!!

If you can read this, you will now know how bad the match is on my 630M antenna

The next thing I do is put the analyzer into the front end of the receiver I built so that I can peak the input filter to be right at 7 MHz.  It turns out I was off by quite a bit!  I made some adjustments and will have to get back to you on whether it makes a difference in receiving actual Amateur Radio frequencies.

I go on to measure my 630M antenna.  I’ve known for a while that the phase of Voltage and current have not been right in sync so my tuning network was off a little.  I had tuned it and thought I had it as close as I could with the scope match.  Turns out as I had my rig expert attached I was able to get the waves in phase.  YEAH!  Unfortunately the magnitudes are not equal, but hey #firstworldproblems.

I plan on working on a better matching network for the 630M set up eventually.  I would sure like it to take up a little less space and I would like to put a little more power into it.  As it stands now my ERP is in the micro watt power level.  It would be great if I could get to milliwatts.  🙂

OK. . . More things to measure. . . I will keep you all posted on what I find!

KF5RY

 

Rig Expert AA-230 Zoom

For sometime I have had a MFJ-259B that I had purchased from an SK estate.  I have treasured the device for a number of reasons.  I knew what I had paid for the device was helping that ham’s family and I felt like I needed to honor his memory by using the analyzer.  Use it I did!  KB5NJD even helped me mod it so it would give us readings down to 470 kHz and I could tune my 630M antenna.  As my knowledge has improved, I came to find that there are a lot of things this model of antenna analyzer does not do and that made me think about getting a different device.

One:  It doesn’t resolve the sign of X.  i.e. is my load inductive or capacitive?  W2AEW has a great video on how you can actually resolve the sign of X using a smith chart using an MFJ 259B style analyzer.

Two:  The oscillator in the machine is not particularly stable in my opinion.  i.e. what freq I was measuring was in doubt by up to 20hz.  This isn’t a deal killer for measuring impedance in the field, but is frustrating in a lab environment.

Three:  The freq. knob is too sensitive in my opinion.  I suppose it makes sense given the tuning range within each band the analyzer covers, but I wanted a little more precision.

Four:  All it provides is Freq (approximate as noted above), SWR, R and X (unresolved whether it is positive or negative.)

Again — As a new amateur, it is perfectly adequate as an antenna analyzer.  But I wanted something a bit more capable.  As it turns out a friend has an AA-600.  He was showing me his conventional transformers and how he could measure the frequency response with the AA-600.  Not only will it define the sign of X, this thing draws a Smith Chart.  It will auto sweep over the entire spectrum of the oscillator enabled on your machine.  You can do live measurements where it will show you the rectangular format of impedance and the vector form of impedance.  This is a genuine scientific instrument.

Now the question is what frequencies should I cover?  I genuinely only have an interest in HF, BUT satellite contacts are interesting. . . and I’ve recently started doing some VHF fox hunts with a local club.  At some point I’d really like to build some kind of 2M yagi.  If I was doing satellite contacts, it would be ideal to have a 440 beam as well, but the cost differential and the likely hood I would ACTUALLY build such a thing. . . I’ll probably just by a satellite antenna, it’ll be close enough.  🙂

If I decide I really want to experiment at 440 MHz I can always up grade later.

 

KF5RY