Function or RF sig gen for alignments

Discussion in 'Technical' started by W6MQI, Dec 17, 2016.

  1. W6MQI

    W6MQI Member

    What would be best to have for receiver alignments a function generator or a RF signal generator? Right now I have an Eico 324 not the most accurate instrument around and after a good hour of warmup time its fairly stable, but unit does suffer from microphonics. Been looking at some of the older military sig gens, some older HP, and Fluke sig gens, and a few of the new function generators available today at reasonable prices. I need something that goes below 100Khz, with the ability to modulate the signal as well. What's the plus's and minus's between the two types?
     
  2. W5HRO

    W5HRO Administrator

    The best thing to use is a modern PLL RF signal generator, but they are fairly expensive for the average ham to buy.

    I use an old tube-type Heathkit IG-42 RF lab generator and I think you can still get them on eBay cheap. It does have the modulator. What I do is use a frequency counter with it. I just use a BNC divider from the generator to the counter and then use an additional selectable Wavetek attenuator from that to the receiver under alignment. The reason is the counter often requires more signal than what you want going to the receiver during alignment.

    IG-42 Generator
    IG-42.jpg

    Selectable Wavetek Attenuators
    atten.jpg
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  3. W6MQI

    W6MQI Member

    Thought about maybe using one of those voltage regulator circuits from the 303 project inside the 324 for better stability might be wasting my time though.
    Those are nice attenuators did you get those off Ebay?

    Picked up a new 10Hz- 1.3Ghz frequency counter last week UPS dropped it off Wednesday in pieces so it needs to go back for an exchange I was supprized UPS has done real well for me in the past.
     
  4. W5HRO

    W5HRO Administrator

    No, those came from a shop way back when I use to be just an RF tech and worked in screen rooms. It was stuff they were going to throw away, etc. Back then I use to drag home anything I could get.

    atten2.jpg
    I cannot stand UPS. I always select USPS Priority Mail now-a-days instead. It's faster and much more reliable. Remember way back when UPS went on strike and USPS had to pick up the slack? They proved they could do it better than UPS so UPS has never been the same since. UPS sucks so it's not surprising.
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  5. NewWave

    NewWave Member

    What the best Signal Gen. is, i don't know.
    I use this one, it runs until two MHz. with all possible functions including sweep, displayed by LCD.
    And was made in the "Brexit" Country..


    signaal gen.jpg
     
  6. Mikeinkcmo

    Mikeinkcmo Member

    There are a couple old generators that are stable enough for serious work, one being the HP 606 and the other, any one of the URM-25 variants. There are also some Boonton 102/103 series synthesized generators that can be had for not much money.

    I wouldn't advise trying to use an audio or function generator for alignment purposes because they usually aren't anywhere near stable enough for the job.

    Finding a good "late" generator for anything near reasonable money, is a full time project in and of itself. A fellow unloading a trailer load of stuff at Dayton a couple years ago had a HP-8657A in his hands when I walked up, and I got (stole) it for fifty bucks. They're out there just keep your eyes open.

    Mike
     
  7. W5HRO

    W5HRO Administrator

    I almost bought an HP 606 more than once back in the early to mid 1990's when I started getting all my National receivers. Tucker Electronics in Dallas had featured them in their catalog dirt cheap because they had acquired a large stockpile of them. I called them a few times because I wanted one that had been factory reconditioned and they did have a few, but the price was much higher, like around $1,000. At the time I had spent so much money on Peter Dahl transformers for the HB transmitter that I kept holding off until I eventually moved out here to California and blew everything off. Now Tucker is all sold out of them, but they still pop on eBay for $100 and less, but many are being sold for parts only, as-is.

    Anyway, that's a good generator with minimal drift after warm up. If you keep a frequency counter handy they will work fine. I worked in an Avionics shop in Tulsa at the airport for a couple of years and we had one for aligning HF, MF and LF stuff. Aligned a lot of old ADF's with it.
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  8. NewWave

    NewWave Member

    If.... If I had more money to spend for my hobby, I like to buy nice equipment instead to use homemade generators...But unfortunately.
    Some years ago I was looking for an Generator from 0.1 - 10 mhz or so with some drive power on the output connector, but I didn't find it for an acceptable
    price, so I made my own one.

    This one Runs from 1 Hz. to 50 mhz. with sweep function, IF setting and more things.
    The DDS output was +/- 8 volt peak, and was enough to drive one cheap (1.20 Euro) TO 220 mosfet driver who gives me now 0.1 - 5 Watt on 50 Ohms and a nice Duty Cycle from 0.1 - 10 mhz. and without tuning !!

    Useful for tube drive during experiments. Last time I use it to drive 4 big fets on 7 mhz with over 10 NF gate capacitance .
    This small iron and HF closed box runs by 10 - 30 Volts and is useful for almost all experiments.

    It looks simple, but it works !!
    . dds4.jpg dds3.jpg dds2.jpg dds1.jpg
     
  9. W6MQI

    W6MQI Member

    Well the business bought me this toy one last tax right off for 2016:biggrin:
    Kinda over kill for my needs but what the hell.

    20170128_185419.jpg
     
  10. NewWave

    NewWave Member

    That is what i mean the real equipment..Nice!!