Now that the dust has settled, I wish to post my sincere thanks to Roger, for bravely putting forward a different vewpoint, originating a discussion that, in perspective, I think made all the readers appreciate the value and the usefulness of the information today easily and freely available on Internet to us all. The perfunctory pinch of salt being always well advised.
This said, I wish to convey the following information, that I judge to be very important
, even if it will appear obvious to people in the know. The ideal instrumentation for amplitude testing a passive filter is Tracking Generator + Spectrum Analyser, equipment costing upward of $1,500 /3,000, an expense out of proportion for any ham/hobbyst.
1) as far as the Spectrum Analyser is concerned
, we have the RSP-1A and/or the RSP2 and/or the RSPduo PLUS the EXCELLENT RSP-SAS software being developed by Steve (whom I do not hesitate to call our Benefactor) which I have used in the Filter threads. A new and far more complete version of the RSP-SAS software should be available very soon, placing this set-up on par with much more expensive equipment.
2) as far as the Tracking generator is concerned
, Steve and others are at work to produce a workable unit using an existing synthesiser board. But what can be used as a substitute in the meantime? The obvious reply: a wideband Noise Generator.
3) After the discussion with Roger et al, I have spent the last three days roaming over the Internet to find a Noise Generator which could replace the presently discussed BG7TBL. I can only conclude what I already knew: THERE IS NO REPLACEMENT AVAILABLE because all that is available is either too expensive, $600 and up, OR does not have a power output even remotely approaching that of the BG7TBL, e.g. -40 to - 50 dBm, which is ideal for passive filter testing. See the second post of:viewtopic.php?f=5&t=3352
So the conclusion is: if you need to sweep passive filters and you do not wish to sacrifice an arm and a leg, for the time being use an $15 Noise Generator BG7TBL, fed with a supply voltage of 9 V. If you need a precise wideband assesment of amplitude, first make a screen photo of the generator's output connected to the RSP-1A thru a suitable attenuator. Then do your measurement and apply a suitable correction.I really hope someone will come along, explain that I am wrong and SUGGEST A MORE SUITABLE REPLACEMENT even costing $100 to 150 ( I wish to ruin myself!). Nothing would make me happier!