Function Generator advise - Page 1
Forum section: electronics / beginners

author: hirada
author_rank: Regular Contributor
timestamp: September 28, 2020, 09:55:45 pm
content: Hello,I am on my quest for a function generator, that is capable of permanently delivering an amplitude of +/-15V into a ~1k load, preferably up to 1MHz. Is there such a thing?I do not need arbitrary waveforms, I'll be perfectly happy with your ordinary sine, square, triangle and saw wave, but would certainly fancy AM, FM and PM. Sweep is a must, but standard anyway, I suppose.However, here's the catch, despite it's anticipated rather moderate use, I want some quality/reliability. Or dependability, however you put it.F.e. for the Uni-T UTG 9005 I have read multiple reports of failures (despite it not meeting my needs anyway), but that kind is something I would like to stay away from, even if cheap. Generally, I would prefer to stay away from made in red china, if realistically possible at all.It certainly does not have to be made by swiss fairies during full moon, just a solid workhorse, the disappearing middle way. Also no need for hyper precision.Many a datasheet I have tried to read specify the Vpp into open circuit. I am not sure, what that exactly means, therefore for me that reads as if nothing/no load is connected at all, except a MOhm multimeter maybe. Fine, but if that assumtion is true, what is the purpose of this figure? The venerable Philips PM513x or Toellner 770x come to mind.So any recommendations I might consider?Thanks

author: bob91343
author_rank: Super Contributor
timestamp: September 29, 2020, 05:43:56 am
content: I have a few old function generators that might work. I would have to investigate the specs. But I have three, a Wavetek, an HP, and one that might be called Interstate.

author: David Hess
author_rank: Super Contributor
timestamp: September 29, 2020, 08:14:56 pm
content: Quote from: hirada on September 28, 2020, 09:55:45 pmFew function generators support that high an output, often because their output range is divided between the waveform output and DC offset.An old Tektronix FG501A (2 MHz) might do it; I have it listed as >30 volts peak-to-peak into an open load and better than 15 volts peak-to-peak into 50 ohms.Some of the old HP function generators had a high output option to extend their output voltage range.Unless something like the above is suitable, I would look into designing and building a fixed amplifier which could be used with any function generator.

author: hirada
author_rank: Regular Contributor
timestamp: September 30, 2020, 08:55:42 pm
content: Quote from: David Hess on September 29, 2020, 08:14:56 pmThanks, I was afraid of that. So I'll move on to finding a suitable opamp in another thread.

author: KK6IL
author_rank: Regular Contributor
timestamp: October 06, 2020, 12:21:58 am
content: Function generators are specified with the output voltage into an open circuit as it is unknown what load the user would be driving. Most are specified as 50 ohms output in which case the output voltage would be half of open circuit when loaded with 50 ohms.Some of the older Wavetek generators are specified as 30 V peak-peak open circuit. These include the Models 11x (110, 111, 112, 115, 116. Different models have different added features, sweep, etc), 14x, and 19x. Models 13x,16x, and 18x are 20V P-P. The models 11x are actually 32.5V P-P open and 30V P-P with a 600 ohm load unless modified for 600 ohm output, which would, of course, make the output 16.25V. Find the manual on line for the specific generator you are interested in. Some models support DC offset, which when enabled, reduce the maximum signal output before clipping occurs.

author: hirada
author_rank: Regular Contributor
timestamp: October 06, 2020, 11:35:12 am
content: Quote from: KK6IL on October 06, 2020, 12:21:58 amThat would be perfect. As 30Vpp into open circuit I have found a plenty, but into 600 Ohms that would hit the nail. I'll be investigating into those. Thanks very much again!

author: alsetalokin4017
author_rank: Super Contributor
timestamp: October 07, 2020, 02:37:21 am
content: I still love my old Interstate (Racal-Dana) F43 "high voltage" function generator. 40v p-p into 50 ohms. Up to 4 Mhz. But no sweep capability unfortunately. I think they made another version that did have sweep but I'm not sure if that one could meet the voltage requirement.

author: floobydust
author_rank: Super Contributor
timestamp: October 07, 2020, 02:48:44 am
content: I got a B&K Precision 4011 (like pic) rescue from landfill. They have some good models to consider.People laugh at me for having some older gear but the output can do over 20Vpp (10Vpp into 50 ohms) and good to 5MHz. The 4011Ais newer.

author: edavid
author_rank: Super Contributor
timestamp: October 07, 2020, 02:53:37 am
content: Quote from: alsetalokin4017 on October 07, 2020, 02:37:21 amThe Racal-Dana F47 is a high voltage model with sweep.

author: ledtester
author_rank: Super Contributor
timestamp: October 11, 2020, 06:19:05 am
content: NFM just posted a video on upgrading an HP 3325A with high voltage output:https://youtu.be/J0aaEC-RoEc