Heathkit IM-4180 Deviation meter

[xrunner]

Thought I'd start a thread on this device. It's a classic Heathkit FM deviation meter. I've never had one, but I've been wanting to get one for a while. I plan on cleaning it up and calibrating it per the original manual. Will be posting more pics when I get it - the one you see here is the one I bought off Ebay, but it's not in my hands yet. 

[mojoe]

Yes, nice piece of gear. I have one packed away, that I got a few years ago. I've never fooled with it, as soon after I got it, I bought an HP service monitor. Some day, I should dig it out and see if it works. Just curious, how much did you epay for it?

[xrunner]

Yes, nice piece of gear. I have one packed away, that I got a few years ago. I've never fooled with it, as soon after I got it, I bought an HP service monitor. Some day, I should dig it out and see if it works. Just curious, how much did you epay for it?

$61 plus shipping. I think I got a good deal. I should get it Monday, and I'll first test it to see if it is reading OK, then do a calibration and take some pics. 

[mojoe]

$61 plus shipping. I think I got a good deal. I should get it Monday, and I'll first test it to see if it is reading OK, then do a calibration and take some pics. 

Yes, I'd say you got a good deal. Good luck with the cal. As usual for gear this old, you may need to replace electrolytic caps.

[Electro Fan]

Congrats on the Heathkit deviation meter.  In looking for info on the Heathkit in particular and FM deviation meters in general I came across these (maybe not quite the utility and definitely not the cool factor of the Heathkit but maybe interesting):

http://www.rtl-sdr.com/measuring-frequency-deviation-fm-transmitter-rtl-sdr/
http://www.rtl-sdr.com/understanding-fm-deviation-modulation-index-and-sideband-theory-with-an-rtl-sdr-dongle/

http://www.sillanumsoft.org/prod01.htm
http://www.sillanumsoft.org/intoduction.htm
http://www.sillanumsoft.org/new_page_2.htm
http://www.sillanumsoft.org/news.htm

[mojoe]

If you Google a bit, there are several circuits for tapping into the discriminator output of a scanner to make a deviation meter. You can also use a scope to measure it.

[xrunner]

Got the meter today. At first it didn't work at all, but after numerous button pushes it started to respond. The person that built it seems to have done a very good job. It's going to need a good cleanup and electrical checkout. I got it to tune to a 2 meter signal at 145 MHz, which was transmitting a CTCSS tone (subaudible tone). It read the deviation as ~750 Hz, which is in the believable range for a CTCSS tone, so that's good for starters.

So next I'll have to take it apart and do the complete cleanup and re-cal. Stay tuned (no pun intended). 

[xrunner]

Found a minor problem with the construction. You have to adjust a coil and capacitor during the alignment. There are two holes in the metal shielding to use for this alignment. One is for the coil and one for the cap. The coil has a hole in the board so you can get to the slug. However, as you can see from the pics, it's impossible to tweak the cap from the hole, because it's been mounted on the wrong side of the circuit board. It probably seemed logical for all the components to be on the same side of the board, but the assembler probably zipped through the construction on that part once he got going and didn't pay close attention to the assembly instructions.

So, I'll be removing it and re-mounting it on the opposite side, so it can be adjusted per the instructions.

[PA0PBZ]

However, as you can see from the pics, it's impossible to tweak the cap from the hole, because it's been mounted on the wrong side of the circuit board.

I see a hole in the PCB, or is that just my imagination?

[xrunner]

I see a hole in the PCB, or is that just my imagination?

Imagination - no hole. Besides, even if there was a hole, you can't adjust the capacitor from the bottom ... 

[AF6LJ]

That is an easy fix.

It looks good inside,
more pics please.

[PA0PBZ]

Imagination - no hole. Besides, even if there was a hole, you can't adjust the capacitor from the bottom ... 

Never mind, I was not reading and looking at the coil 

[xrunner]

Never mind, I was not reading and looking at the coil 

LOL no problem. 

It looks good inside,
more pics please.

Have a few knobs to put back on, but here you can see it performing after a full cal per the manual. Hope you can see that it indicates the correct 3.0 kHz deviation as seen by the Marconi's setting's.

I'm very pleased with this little unit. 

Damn I wish Heathkit would start making new test equipment kits. 

[AF6LJ]

Looking Good.

[xrunner]

During calibration you are told to connect a frequency counter to the RF input, so you can monitor a 25 MHz signal as the dial is turned up to the 50 MHz point. It states that "some freq. counters may display multiples of the 25 MHz signal" so to use those multiples to calibrate it if your freq. counter does this.

I decided to connect my DSA815 to the RF connector, and you can clearly see the 25 MHz harmonics the deviation meter generates. I found it easier to just use these to determine how the initial calibration adjustments were going.

[xrunner]

All done. 

Re-capped the electrolytics and finished cleaning up the knobs and case. Another nice addition to my test equipment family. 

[AF6LJ]

Very Cool..
It's always to see a Heathkit put to good use.