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Reviews Categories | Ham radio kits | DC Kits WBA-1 Wideband Preamp Help


Reviews Summary for DC Kits WBA-1 Wideband Preamp
Reviews: 1 Average rating: 5.0/5 MSRP: $$20
Description: Wideband preamp for receivers and test equipment
DC to GHz
Product is in production.
More info: http://www.dckits.com/
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N4UE Rating: 5/5 Dec 1, 2008 15:04 Send this review to a friend
Great little preamp!  Time owned: 0 to 3 months
This might get a little long, but it just goes to show 'ya, I can screw up almost anything!!!

Like I told the owner of DC Kits, it's great to eat some 'humble pie' on occasion. I ate the whole pie this time!!
These are nice, simple kits based on the MAR-6 MMIC. Yep, these guys are small! However, that is NO problem... The kits are very simple and contain few parts.
I have been a Ham since 1962, have a Degree and everything. However, due to the simple nature of the kits, I screwed up!! I have built many Heathkits, Elecrafts, Idiom Press, and homebrew a lot of 'stuff'. I also restore boatanchors, both tube and solid state. I have 3 well equipped test benches with HP, Tek, etc.
I purchased 2 of the kits and believe I may have applied the incorrect DC voltage to BOTH of them during initial testing, 12VDC versus 9VDC. I am not 100% sure of this, but 'kinda sure'....

Anyway, Gary Clifton, generously sent a replacement pair of MAR-6s.
Note: I used an ESD safe, low wattage iron to assemble the kits, using minimal heat.

While I was waiting for the new ICs to arrive, I made a small change to the small project boxes that house the amps. I added an on-off switch and a red LED to remind me to turn off the preamp when done. I have several other wideband preamps I use for the input of my various counters, and have had great results.

Anyway, I get the new ICs and the amps STILL would not work. I looked over these very simple strip-line amps for what seemed to be forever.
One amp not working would be bad, but like I told Gary, this was just nuts. I should have added 'stupid', ME!!

I sent the assembled amps back to DC with some extra $ to cover return shipping. Today, I got the amps and it appeared that all they did was remove my LEDs. (and returned my MO for return shipping) Hummmm, the LEDs were connected to the RF side of a dropping resistor and choke. (I did that, since that was a 3 VDC point, and I wouldn't need the usual dropping resistor).

Yep, the light bulb went off! Even though I had looked at the schematic and instructions for what seemed to be 100 times, I realized that the dropping resistor ALSO develops the amplified signal across it!!!!
The first time, I may have 'overvoltaged' it, but the second time, adding the LEDs killed the output.
No, this did not hurt the ICs. I verified this today. I simply went to the 9 V battery with a 1K resistor for the 'pilot light'....

Great little preamps. They have a NF of 3 db at 1GHz!!!!!
By using different values for the input and output coupling caps, you can optomize the frequency range.

tnx fer listing!

ron
N4UE
 


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