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Old 5th December 2017, 03:59 PM   #141
w5jag is offline w5jag  United States
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Join Date: Feb 2007
Location: Arkansas
I'm going to have some LC circuits that I have no realistic way to accurately measure or characterize, so I thought I would try to select components as close to the calculated values as reasonably practicable, as a substitute.

I got an LC-100-A LC "meter" that has been on the market for a few years now from $13-25, or so, depending mostly on how fast you want it. I had been using a dip meter, but it is tedious, and ball park accurate at best. This gives only inductance, no other parameters, but for $20 ish, it's a bargain, I think.

Once calibrated ( easy ) this thing will measure a sack of coils faster than Jack can jump over a candlestick. It looks to be useful for all RF type coils. Pics are shown measuring a typical small value slug tuned inductor, and an air coil. I have not used it for C, yet.

I should have semi suitable coils in my parts inventory ( may not be shielded, though ), so, next stop, solder.

Win W5JAG


edit: one other question: the main RF unit is planned to be in the trunk. In Arkansas, the temperatures can be extreme - below 0 F in Winter, and well past 100 F in Summer, with almost 100 % humidity. I think can make most of these small value inductances as air coils. Would that be preferable from a temp stability standpoint, as opposed to a slug tuned coil?
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Last edited by w5jag; 5th December 2017 at 04:29 PM.
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Old Yesterday, 04:44 PM   #142
w5jag is offline w5jag  United States
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Join Date: Feb 2007
Location: Arkansas
I had been wondering where the Tellurian filters were - had to go back home for a few days last week and found them in an envelope in a stack of junk mail. Mine came with gold plated leads.

Quote:
... Mini circuits do some great broadband MMICs which are 50 ohm input, or very easy to match to that...
I found a few MMIC's in my junkbox - NEC upc1651G, a 5 volt part, but looks ok otherwise; about 5 dB NF and 19 dB gain at HF. The sheet I have says nothing about matching in / out. Looks like it's a 1983 ish device. No apparent way to apply AGC.

What do you guys think of these modern IC mixers, like this AD831 example:

AD831 high frequency RF mixer drive Amplifier Module HF VHF/UHF 0.1- 500MHz | eBay

Pretty high Ip, but seems noisy from looking at the datasheet, not sure that would matter much at HF. A little less cost than an SBL-1 and if I am looking at the sheet right, matching in / out is not especially critical.

The Analog Devices eval board is over $100 at DigiKey, so these boards seem like a deal. I would remove the sma connectors.

Still on mostly holiday staycation at the lake, so, no hardware progress on any project.

Win W5JAG

Last edited by w5jag; Yesterday at 05:00 PM.
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Old Yesterday, 11:20 PM   #143
gerhard is online now gerhard  Germany
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Join Date: Oct 2005
Location: near Stuttgart, south Germany
I have no experience with these; Gilbert cells are not praised for
their dynamic range. But it is a cheap test and easy to get something
running in the first place; optimizing can be done later if needed.

I have ordered a RedPitaya yesterday; that should take care of
the basic RX & TX from DC to 60 MHz, and it also can be used
as a simple scope, spectrum analyzer and signal generator.
A lot of value for €310.

I'll then build transverters for 144 (adding 100 MHz) and for
432 (adding 2*2*100MHz). The userinterface/firmware will
be HPSDR, someone has done that already. Thus the
total effort shrinks to sth. that can be done in finite time.

BTW for the inductance measurements above, one cannot
ignore the cables with the gator clips. That must be minimized.

73, Gerhard

< SDR transceiver compatible with HPSDR >
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