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Jim,
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Any guidance as to maximum signal level for sweeping these Drake filters? Thanks, Jerry, N4JL -----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Jim Shorney Sent: Wednesday, March 6, 2024 12:22 PM To: [email protected] Subject: Re: [DRAKE-RADIO] Drake SL-2300 2.3-5645kHz Filter Testing Wes, Comments inline below. On Wed, 06 Mar 2024 07:03:50 -0800 "Wes Winkler via groups.io" <wewinkler@...> wrote: I got a couple of Drake SL-2300 2.3-5645kHz Filters at a swap meet and amcontemplating testing them with a NanoVNA.? I have three concerns. concerned about damaging the filter due to the signal input signal level. Yes. I have done it with several TR7 filters with both a NVNA and a Midnight SNA. They both agree closely with sweeps done with two different HP 8594E spectrum analyzers with the tracking generator option. You could use an inline 50 Ohm attenuator on the NVNA output if you are really worried about the signal level but I have had no issues. 2) I reviewed the TR-7 manual but it not immediately obvious which is theinput, and which is the output of the filter. The filters are symmetrical. It doesn't matter. If you really want to know you can trace the signal path on the block diagram and the schematics to figure out which port is which by visually inspecting the filter board. 3) An idea of what the input/output impedance termination should be?? Imay need matching transformers for the Nano VNA test. 50 Ohms. You can directly connect to the NVNA. Attached are some samples done within the past couple of months of NOS eBay filters. One is a screen cap of an Inrad 4 KHz, the other two are sweeps of a late production Drake labeled SL2300 done with nanovna-saver software in Linux. You can also bench test the filters from your radio without taking them off the filter board. All you need is a source of around 10 volts to activate the filter you want to test and a source of -4 or so to bias off the unused filters. I used by bench supply for the + voltage and a 18650 lithium-ion cell for the - voltage. 73 -Jim NU0C |
