Window Transition Cable

Hi all,
I just stumbled across this video.

VBR from Ivan

Hello Ivan,
Yes, I am really enjoying life. I cannot complain, even though I m English  

Yes, I saw the new user you activated. Thank you very much.

Ok on the copper foil. But if you need any then the offer is always there.

T be perfectly honest, I ould prefer that you use the link "https://sm0vpo.com/antennas/cable_transition.htm" (or "https://www.sm0vpo.com/antennas/cable_transition.htm") but it does not make any difference at all. Use whichever link you feel is the easiest.

If I add a new project then I can update sm0vpo.com quickly, but like the transition project, altervista had to wait a while. Altervista is also a limited server in that there is little space on there, that is why there are no PDF files there, all the files are on www.sm0vpo.com. The altervista link to the files points to www.sm0vpo.com/_pdf.

Now that the server has been upgraded, certificates are in place and you can link to individual projects and files, the sm0vpo.com server is now the most reliable (IMHO). The link to the PDF directory, for example, used the IP-address, so every time the ISP changed the IP-address then the link stopped working. Now that has been fixed with the text URL.

Note that if you use http://www.sm0vpo.com (port 80) or https://www.sm0vpo.com (port 443) then the page is still available since I have both ports open. In both ports the "www" is also optional. These problems were the reason I created the altervista server.

My son-in-law has done a LOT of work to get me a new up-to-date server and using the latest Abyss server revision. I can now create secret directories and password-protected directories for sharing files and programs for specific people, or even my own personal documents when I am not at home. I can also manage the server using remote-desktop from the office. Before I used to have to login to the server using SSH or SCP to move files there. Now I can have two windows open and just copy/paste between them. No LINUX commands, nada

I have uploaded the window transition files and updated Altervista, so it is now a mirror of all current projects on HHH. If you find any duff-links or differences then please let me know.

Very best regards from Harry - sm0vpo

Hi Harry,

I am glad you enjoy your life and work. You are really active!

About the account activation - you are welcome! I have just activated another one.

Thank you for your kind offer of copper foil, but do not bother. I will better find a local source. The difference between copper and brass should not be great, I hope. I even considered an aluminum base (kitchen Al foil), but I discarded the idea due to soldering problems.

I wrote a small article about the topic in Czech for the OK QRP INFO bulletin. I mentioned your solution with the link "http://sm0vpo.altervista.org/antennas/cable_transition.htm". Will it work or should I change it before the bulletin is printed?

I made the impedance measurement with my Vector Analyst VA-1 and it seems to work O.K. I measured the inductance of a shorted sample, the capacity of an open-end sample and calculated the characteristic impedance Zo = SQR(L/C)  This method is easy and gives reasonable results according to my experience.

VBR from Ivan

Hi Ivan,
1 - Thank you for enabling the new account the other day.

2 - Your results are very good. I am so pleased that you have had such success. It was a good account that you wrote.

If you want thin copper tape that I used then let me know and I can put a couple of metres in the post to you?

I just used a VSWR meter when I checked mine. I also used a signal generator that has a 1-Watt output, as well as my HF rig. I used the generator first just in case the VSWR was rubbish.

BR Harry

Hi all,
I finally got copper strips from China and made some samples, cca 0,5 m long. I found that the copper strip 40 mm wide and 0,2 mm thick was very hard and would not bend inside the window frame, so I had to use the brass foil again. Brass has slightly bigger losses, but should not affect the characteristic impedance much.

I stretched a 40 mm wide strip of brass foil, then 19 mm wide teflon tape (0,2 mm thick, used by plumbers) along the center, a narrow strip of copper foil (made for PCB repairs) and sealed this sandwich with some packing tape (type is not critical, but it must be dielectric) - see the photo. The wide strip is usually grounded, so its bottom side may be left bare or covered with the same packing tape, as wanted. When I used 10 mm copper strip as the inner conductor, I measured 51 ohm characteristic impedance, unbalanced. It matches well a 50 ohm coax. With a 5 mm wide strip, the impedance was 79 ohm, it might be suitable for a 75 ohm cable. The measurement was done at 15 MHz. I could not test the maximum power, it also depends on the SWR.

The thickness of the sample is less than 0,4 mm and bends easily. The inner conductor, which connects to the center conductor of a coax, is quite fragile, so the connection must be reinforced with hot melt glue etc.



VBR from Ivan OK1SIP

Hi all,
my design should have its characteristic impedance in the 40 - 60 ohm range according to calculation. I measured 172 ohm instead.    This probably means the round wire should be replaced with a wider strip of conductive foil. I ordered some copper foil and I will make another sample. And I must check my RF bridge, I have not used it for a long time due to my illness.

VBR from Ivan

Hi Ruud,
I found  three produts suitable also for TX, all have 50ohm impedace and SO-239 (UHF) connectors. They are
Comet up to 100W PEP on HF;
Diamond up to 150W PEP on HF, 50W CW;
from China power unknown, cheaper, maybe for RX or QRP only.
This list is not exhausting. A common problem with commercial solutions is the price.

The maximum power may be a problem with types designed for satellite reception.

I am working on my own design, see the thread in Homepages feedback.

VBR from Ivan OK1SIP

I have seen this principle many years ago. It was used for feeding the cable from a satellite dish into the house through a window.
So with a bit of luck, these 'feedthroughs' are still commercially available (probably with 'F' connectors), with a good plastic seal around them.
And if this solution if good enough for signals from a satellite LNB, it must be good enough for HF!