ISO Pixel RF PRO 1b schematic

[WA2SQQ]

I’m looking for the schematic for the preamp used with Pixel RF PRO 1B loop antenna. Dx Engineering bought them from Pixel who has a policy not to share schematics. Specifically I’m looking for the identity of the devices used for the amplifier.

I suspect that an indirect lightning hit took out one of the devices.

[Pete, WA2CWA]

I've never seen a service related document or schematic for the Pixel preamplifier. I don't see why the manufacturer would release that information. Can't you open it up and check for markings on the devices? Might also check with various reviewers to see if any of them as part of their review opened up the preamp box and mentioned what devices were being used.

[WA2SQQ]

The entire board is coded with some type of a semi-clear coating I guess to protect it against possible moisture damage, i’m going to try and clean a few of the components to see if I can remove that coding and I’ll likely have to use a microscope.

[Steve - K4HX]

Didn't those use Clifton amps? Maybe you could find a schema for one of those. Sadly, the guy behind the company has passed away.

[Opcom]

Another individual said the same - that they used those Clifton Norton amps

-two kits are/were available online, the manuals are archived in a few locations which putting the model numbers into google will lead to.
Models Z10040B (2009 & though hole) and Z10042B (2010 & SMT).
These are made of discrete transistor circuitry with broadband transformers.

I was told another thing by a sales person at ham-com where I bought my PRO-1B - that they used broadband IC 'telecom line driver' amps capable of a few (tens of?) mW output power which made them more robust in RF fields if near the TX antenna -which could happen. I've never opened mine to look at the amplifier board, and it's up on a pole.

There was something in the manual about the reason for turning the loop preamp off during transmit was not to protect the preamp but to keep the high RF output from blowing up receiver front ends. That sort of statement could apply to either a broadband driver IC or a discrete circuit.
It was also said that if the loop was close to a high power antenna, then enough RF could go into the loop amp input to sort of power it and then rf would come out through the output of the amp to the RX.


here is something similar using the AD8007 IC. DX sells it as a buffer amp for I.F. just saying there are ICs out there.
https://static.dxengineering.com/global/images/technicalarticles/dxe-z10000u-kit.pdf

[N4LTA]

I used several Clifton amps that I bought when he was still in business along with his active antenna design. They were purchased by DX Engineering and they sell the preamp that I used with the antenna. I purchase one last year and they seem to be the same design. I made a board for his circuit and have most of the parts to build it. I plan to build a few after I get back in my shop. The one that I purchased from DX Engineering is installed on the antenna about 150 yards from my house. Not sure if it is still working, but is was before the fire in April.

I have the original documentation for the amp. One stage used complimentary SMD transistors that are not available but I found a set of transistors that have a bit higher GBP and similar characteristics.

I can send you the data that I have.

Pat
N4LTA

[N4LTA]

Here is some data on the Clifton Labs active antenna and coupler:

https://www.okdxf.eu/files/Z1501D%20Instruction%20Manual-01.pdf

https://www.okdxf.eu/files/Z1203B%20Rev%2002%20Manual.pdf


Pat

[Steve - K4HX]

Good stuff Pat. Thanks for posting.

[WA2SQQ]

OK, so I managed to get a p/n of the device - "FF" "P11" It's Q101 & Q102 in the attached photo. I found several references to SMD's with these markings, but the description or case styles don't match up. DX Engineering wants $140 for the estimate / repair with an estimated 30 day wait until they can look at it. $179 buys me a new one, from in stock.

The preamp appears to use 4 of these. Traced the signal through and both of these in the input stage are open, so that's my problem.

[N4LTA]

Mine uses an NPN PNP complimentary pair of transistors in the high dynamic range output circuit. The NPN is a BFQ19 and they are available for 75 cents. The PNP is the problem. It is a BFQ 149 115 and these are very hard to find. I have four that I paid $6 each for. I have looked for something similar but have not found anything. These are 5 GHz devices.

Pat

[WA2SQQ]

So the p/n is BFQ 149 115 or are these two devices that can be used? Just curious how you discovered the part numbers?  Now to figure out which one is which?

[WD5JKO]

I would use the DVM diode check on the transistor PN junctions, and do so in circuit. Try to reckon with schematic where the diode test is flaky.
Also, from the image posted, the solder connections look very marginal, and could be all or part of your problem. Sure, lead free solder is not shiny, but what I see
is cracks, and crevices in the joints. A quick reflow in critical areas might be helpful. I repair boards all the time, and for me, it takes my 2.0 bifocals, a magnifying lamp, and another 2.5X lens.
With that amount of magnification, even good joints look iffy....From what I see in your image, with + selected, is really bad at some spots.

Jim
Wd5JKO

[N4LTA]

The PNP is BFQ 149. Sometime I see it designated BFQ 149  115 and I think but am not sure that the BFQ115 is an equal device. Some guy in Kentucky has them on Ebay for $6.

Pat

[WA2SQQ]

 I just got the microscope out and verified that all 4 devices are marked FF P11
If I can believe the markings, all 4 devices are the same
Going to try he testing you suggested. Checking the solder now ...

[N4LTA]

Then if they are all alike, they are likely NPN BFQ 19. Mouser has then for 79 cents. I can send you a couple if I can find them. I have plenty.

Pat

[WA2SQQ]

Let me verify that they are MPN. I appreciate the offer but I have an order I’m going to be placing with Mouser so I can add these in, thanks

[WA2SQQ]

So I verified that the devices are NPN. I checked your BFQ19 and found out that the designator code isn’t “FF”. Did some searching and the BFQ18A has similar specs and its designator code is “FF”, which matches the original devices. $1.09 from Mouser, so I’m ordering 6 PCs. There is an end of life notice, so when their inventory is gone, they will get scarce.

https://www.mouser.com/ProductDetail/NXP-Semiconductors/BFQ18A115?qs=me8TqzrmIYVSffGA4%252BC8jA%3D%3D