How to tune a filter?

Richard Lee

So, what do you think about the $82 gen?

I would like to buy one. But first, I would like to see some review type posts from some Hams..
$82 isn't peanuts to an old retiree.

Anyways, I was thinking about filters last night and I may be able to use my 200 Mhz O-scope
to display the detector diode DC, by using the input to channel A trigger the O-scope sweep..
I could set the sweep time to match the signal gen sweep time.


New Member
The $82 unit looks good for my antenna return loss testing purposes; thanks for finding it! I think I'll order one and some 20 or 30 dB attenuators. By the way, I don't think I'll need a hardware adjustable attenuator as long as I have fixed value attenuators to get the signal level down to where it's not overloading the SDR dongle. The signal can be fine tuned to a reference level with the tuner gain control in the SDR# app.

The O-scope approach sounds good too. But I have very little experience with scopes :)


New Member
I ordered the $82 ADF4351 unit plus some attenuators and cables. When the gear arrives in a couple weeks I'm going to try using RTLSDR Scanner to test the antennas in my airplane.

Here's a transponder antenna I made and installed over the weekend. I hope to flight test it this week. My transponder is only Mode C (altitude reporting) so you won't be able to see me with Plane Finder :). Small aircraft are mandated to install ADSB by 2020 and I'm waiting for prices to come down.

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Richard Lee

It's amazing how small a 1/4 wave is in the L-band..
That wire kinda looks like regular house wire. My advice is to place some of the insulation over those sharp points. (To protect eyes etc).

Looked at the RTLSDR Scanner site and it looks pretty nice. But the comments weren't very encouraging.
The windows install doesn't look very easy either..

I also ordered the $82 ADF4351 today.. :cool: I hope we get some good hardware..
I have not looked at the ADF4351 program yet..
I've been repairing an old Dell 4600 (bad PS), to use with the new stuff.
Once I find a VGA cable, I'll set it up and start installing some of the Dongle and ADF4351 software..
It doesn't look too user friendly..


New Member
Yes, the copper ground plane is #12 house wire; that's what I had on hand :). The antenna is installed under the airplane's floor so there's no danger from the wire points.

I installed RTLSDR Scanner yesterday and got it working after a some messing around. Why do Linux users like the command line? Makes me feel like I'm back in the days of DOS :eek:

I also installed the ADF4351 client app. There are a bunch of settings I'll probably never use. Basic operations (frequency, level, sweep, etc.) look easy.

BTW I'm studying the Technician Class materials and hope to take the test this summer.
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Richard Lee

Kinda reminds me of a Ninja throwing weapon.. :p
Maybe I'm just a goof, but I've been stuck by stuff like that before.

My last painful antenna accident was a few years ago, under the tail of a old 707 jet..
I was cutting, measuring (Time Domain scope) and installing N-connectors on 4 runs of coax. All runs had to be the same length, electrically.
Just about done, and was distracted by loud noise, while ducking under the tail. I was also wearing a baseball cap pulled too low,
and ran right into a fiberglass antenna radome. Cut the top of my head and almost knocked me out! :confused:
No damage to the radome.

I may try that RTLSDR scanner later.. If it's not too hard to install. Is your install on a Linux PC?

Good luck with the Tech ticket. I had one for decades. 1969 to 1982 I think..
I decided to get my Advanced and did 20wpm on the code, so after I aced the Advanced,
I asked to take the Extra, just for fun. Did it real quick, since it was late.. Almost aced it too!
So, I was only an Advanced for about 20 minutes. My wife has her Tech.. Never uses it..

I better get to work on that Dell.. I need to steal a SVGA cable from somewheres.. Security DVR?? Yeah!