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Recommendation for a modern signal generator? - Printable Version

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Recommendation for a modern signal generator? - Jordanbkc - 06-26-2023

I'm wondering about some of the similar generators (Koolertron) on Amazon for around $150. I'm not collecting radios, just trying to fix one or two.

(moved to separate thread by admin)

RE: Recommendation for a modern signal generator? - Ron Ramirez - 06-26-2023

Hi,

I looked at those Koolertrons and considered getting one before I bought my Siglent.

Sure, they cost a lot less than a Siglent (which is also made in China), but are they as good?

I honestly do not know.

I can tell you, though, that this will require inline attenuators, as did my Siglent, to provide usable signals to a vintage radio.

I will let the folks on here who know more about signal generators (looking at you morzh, RadioRoslyn, BrendaAnn, Dale) comment further on this subject. Icon_smile

RE: Recommendation for a modern signal generator? - DaleHCook - 06-26-2023

I don't own any Siglent equipment, but the people who I know who do own some like it a lot.

I buy very little shop equipment new because I like to be able to repair it, thus I have a shop of mostly '60s to '80s Hewlett-Packard, General Radio, and Tektronix instruments.

My General Radio Type 805-C Standard Signal Generator does everything I could need in an AM generator because it has virtually the same specifications as the exciter in some older solid state broadcast transmitters.

RE: Recommendation for a modern signal generator? - morzh - 06-26-2023

Given my experience, anything digital (synthesizer) is good.
Those old tube jobs, while give you the warm feeling "hey, look at me, I am an old school radio tech", in fact do not work well, are not stable, have error between what you set and what you get, and require therefore the use of frequency counter. Which weill tell you that your signal is drifting. Icon_smile

One piece of advice: some folks complain of solid state SG outputs sometimes getting damaged by connnecting them to tubes inputs due to some potential kept by capacitors.
I avoided that by simply connecting back-to-back small voltage zeners right across the SG output (I made an insert for a BNC cable). This will limit any spike to safe levels.

RE: Recommendation for a modern signal generator? - Radioroslyn - 06-26-2023

Last generator (10-22) I got was a URM-25F. Circa Korean War vintage set. Has everything I need in a sg. Two tone modulation up to 100%, well attenuated, great for check sensitivity down to tens of a microvolt, build like a brick privy. Tunes 10KC-50MC. 

So far I have found two issues. The band switch is really clunky and having to tune from one end of the dial to the other. It's tuning when your aligning a multi band set is a lot of back and forth. . The mode switch is intermittent. For $35 I not complaining.

RE: Recommendation for a modern signal generator? - DaleHCook - 06-26-2023

I spent $50 for my GR 805-C, and it took a few days to get it back to the level of specs that it had when new (i.e., like all quality instruments it was shipped with specs significantly better than the catalog specs). The labor (and a couple of 2A3s used as regulator pass tubes) were well worth it.

RE: Recommendation for a modern signal generator? - GarySP - 06-26-2023

Wow ... I thought I hit paydirt when I picked up a Heathkit SG-8. Needs a little longer to warm up to settle down the output drift. Guess I'm just an "old school radio tech". It is just a casual hobby to me. Take care and BE HEALTHY! Gary

RE: Recommendation for a modern signal generator? - morzh - 06-26-2023

Gary

I have both SG-8 (csme for free, restored) and Leader LSG-11. I mostly used the latter until I bought the HP about 6 years or so ago.

RE: Recommendation for a modern signal generator? - John Bartley - 06-27-2023

I bought one of these new over fifteen years ago. It's served me flawlessly ::

https://www.ebay.com/itm/404344957236?hash=item5e24d66934:g:3uAAAOSwXfpkky95&amdata=enc%3AAQAIAAAA4NlW%2FcT%2BsdwMNwOYNQgrjCgO4txPjY4qNjHdJ13fjlhrihApJKbFegPF3uOQnCbnQw4jNPZaTSD%2FU1NVnzG%2BvA2gWfW06HXN38nqxhWKiB30cKuW3qGVSxb8nfwMcI8Zk5UqVmoFud%2Fxldc4fkrh7YtrgCXOQpxsKSZWeNd50RthjBWBmUXxNOCPinRfUyabxHkkDKovIt7pPrHHQD0b57b0nbpy9qJ5StakdTEJgWifjCYcOBltt2qn77Nsp8I%2BgLi1crLaPuKr%2BZ23r%2B34B9YWZZZxs8AKYeI228OTRlBk%7Ctkp%3ABFBMjILkyJ9i

There you go ^^^. New in box from a US based ebay seller with a 99.9% positive rating.

Here's another one :

https://www.ebay.com/itm/325709614791?hash=item4bd5ce4ec7:g:K5cAAOSwXF1kmhHT&amdata=enc%3AAQAIAAAAwC83n0a76I8R7O4vG%2FvvYhoItbpGHOKqDMK5ccDgvL9%2FONB%2FpnLbl4%2BQQ3P22b1LVljvt1YQ0dpzbyQlpbZ5u9jmcYMis90OqRtvRB4eCIvoVZ5pzLutjuO%2BqZOemsSJqe7JUKY0GOCSdR4DKTw1ATv1gFOX%2B3efKNc6SubyMFMlE9Q9gOlKAWNpQi1pXt2ZtpImUEboTTzO%2F3VLgj8qHDAYS9EIs4WZrxRdvUZ85XgjtoUDF7dUgI4IF6p8DSxfew%3D%3D%7Ctkp%3ABk9SR46C5MifYg

cheers

RE: Recommendation for a modern signal generator? - Radioroslyn - 06-27-2023

If you read the manual for the SG-7 & SG-8 they are not designed to be used a frequency standard but to peak an existing setting. In of words they are not accurate at all. There is one trimmer that will adjust the oscillator on all 4 or 5 bands at once. The rest falls where ever. I would set mine @ 460kc so it would be accurate to do some IF alignments. Broadcast and shortwave were within 100kc-1mc or so on the generator's dial. Would use my digital ham rig to check it's frequency output. Or if I was setting the lo I would use a cheap programmable counter to get it spot on, well at least the end points. Wouldn't use one these types of sg above 10 or 15mc.

They leak rf like crazy! Shielding is poor and rf gets out of the cabinet and the cord. It radiates everywhere. In layman's terms it means that if you are servicing a sensitive (more than the average bear). You can't turn the attenuator (it's not shielded) down low enough to prevent overload. 

Mike can tell you that the output waveform is kinda scary. Modulation level is about 30% at best. 

Point is yes you can use these entree level jobs but they do have their drawbacks.                                                                                                                                                                                                                                          https://archive.org/details/sg8signalgeneratormanualschematics/page/n5/mode/2up?view=theater

RE: Recommendation for a modern signal generator? - morzh - 06-27-2023

Yes, the output waveform to the sinewave is like a horny toad to a pussycat. Kinda has the legs and the head, but that's where the similarity ends.

Funny part is, the generated waveshape is perfectly fine, but then they run it through a cathode follower, and that one, somehow, mangles the heck out of it.