Hellenic RF Lab 2M Combiner

email me - [email protected]

I am building a high power multiband VHF amplifier around solid state 1kW Larcan amplifiers. Four modules will be paralleled for 50MHz and two for 144MHz.
For 144MHz I had hoped to combine a pair of modules with the Hellenic RF Lab combiner. It didn't work out quite that way.
Here is the web page for the 1kW 144MHz Larcan amplifiers.

These are pictures of the 2M combiner as received from eBay seller hellenic_rf_lab in Greece.
Very poor workmanship with soldering. Where mounting holes were drilled the sharp burrs remain. No attempt was made to clean up the board prior to shipping.
Note the substitution of a 100W resistor where it should be 500W. This will limit the power of the Wilkinson combiner to only 400W. The ad is rather optimistic at 3kW.
Supplying a 100W resistor instead of the 500W as indicated in the ad is little short of bait and switch.

When the item arrived I immediately started a discussion with the seller, Maria Sfiraki via eBay dispute resolution. She said the 500W resistors were no longer available and the 100W resistor was being substituted. This should have been shown on the eBay listing, not a surprise upon delivery. At first she wanted me to send the combiner back at my expense. This was unacceptable. I asked that the proper size resistor be supplied and it was declined. Eventually she agreed to pay return shipping and promised to send a new combiner with a 500W resistor. Tracking confirmed the combiner arrived in Greece but she would no longer respond to my email. Now she had the combiner and my money. After being ignored for several days during which I sent several email to ask about the status of the item I opted to escalate to eBay customer support. They issued a full refund via PayPal and I expect went after the seller for their money. This was done on the last day at which eBay is able to act and recover funds. I think every attempt was done to remedy the transaction. After discussing with several friends I decided to leave negative eBay feedback. Be very wary about purchasing from this dealer.
I've also submitted a review at eHam.net
I'm not the only one with complaints about quality control or poor communications. Check this message thread at eHam.net.

You can email Maria Sfiraki at Hellenic RF Lab at this address - [email protected]

Here is an email that was forwarded to me. Maria clearly wanted the part returned and had no intention of sending a replacement.
Was it unreasonable to receive a 500W resistor as the ad had clearly displayed?

Dear friend,
My politics is not comments.
I sold one splitter in one person from Canada and i put resistor 100 ohm / 100 watt because all my resistors 100 ohm / 500w They finished.
I accepted full Return money and i paid plus $72 for shipping cost back.
The customer wanted in each case my splitter with resistor 500 watt or will put negative feedback.
I am sorry my friend but i not accept extortion.
Now I have ruled Canada for sales of my products.
This is really the truth.
This customer he could not accept that I will can have the option to not want anymore to work with him and so put negative feedback.
So you must understand that customer has some psychological problem and unfortunately I'm electronic women only and I can not help him.
For any case for my customers not need information for my products know me many years.
For the end sorry for my english is not so good.
Kind regards Maria

The original eBay ad and pictures as delivered are shown below. The seller has since increased the selling price from $259.99 to $289.99 and now $299.99! There has been no mention of substituting with a low power resistor.
She will no longer sell to Canada. My intolerance for garbage has given Canadians a bad name all the way across the world! :)

Click thumbnails to enlarge.

This is the original ad on eBay. I do not understand the her power ratings. However with the 500W resistor, a pair of 1kW amplifiers would be fine.
Wilkenson combiner 2X1.2KWin 2.4KW out 0degree in phase

Check the balancing resistor. It is clearly 500 watts.

This is what I received. Overall a nice design, but workmanship is terrible. Check the gouges in the section by the output connector. This is for tuning. Very sloppy work. Four holes were drilled and countersunk for mounting to a heat sink. The edges around the holes are not trimmed.

The resistor is rated 100 watts. It is clear the board was designed for a physically larger resistor.
The square pads to either side of the resistor are part of tuning the combiner. They have sharp edges and are not flush with the board.
Would you want to operate the combiner at 3kW output?

Output tuning. No attempt to tidy up after running a knife through the circuit board.
Note the added layer of copper at to the output connector. I don't know why this patch was added.

No effort to cleaning up rough edges around mounting hole.

Another sloppy mounting hole. The copper pad tuning squares are haphazardly soldered in place.

Another sloppy mounting hole.

The fourth mounting hole is no better.

Perhaps the most damaging problem is from the etching process. There are holes throughout the traces! You can see the holes in other pictures as well. Quality control is almost non existant.
This will clearly limit the power handling capability of the combiner and for my purpose rendered it useless.

Prior to shipping it back I decided to clean up the rough edges in hopes the seller would supply a replacement 500W resistor.
Here are some more pictures with a ruler to get an idea of dimensions. Maybe you can clone the design and build your own. :)

To be fair, I was quite impressed with test performance of the combiner. RF sweep response for isolation, insertion loss, and 3dB split are very good. She has a nice design, but really messed up on quality control. It would have been so much easier not to pull this sort of stunt from the beginning. I've bought and sold many items online and the vast majority of the time the transaction goes very well. It was terribly disappointing to see such a potentially good device presented in this unacceptable manner.

Here are the response curves.

Input match 1 and 2
Output match
Isolation between inputs 1 and 2
Power split, output to input 1
Power split, output to input 2