Shortened VHF beam

So, did the 5 element Yagi-Uda work with 4 elements only? I know the World wants to know!

Yes, it does work. First I checked with an antenna analyzer the new setup (using dir2 and dir3 as dir1 and dir2 respectively) and I measured a nice 1.1:1 SWR at 144.3 MHz.

Then I mounted it outside and tried some real-life contacts. SWR was 1.2:1, probably increased because of the metallic fence nearby the antenna.

Either propagation was better than one month ago or the theoretical 1dB extra gain on my other 4el beam did help a bit: best DX at 227km with 50W SSB. Not bad for a beam on a balcony!

FT817 external display

I received an email asking if I could develop a simple remote display for our beloved FT-817. It would need to display only the operating frequency.

Greg assumed that given my keypad code it would not be a big problem to implement such a gadget, and he was right.

I have the code ready for real-hardware testing. Now I need to get hold of a LCD display.

I will let YL choose the color :-)

Shortening a VHF beam

In my last excursion in August 2009 I damaged the boom of my homebrew 5 elements VHF beam. The boom broke at the 2nd director hole, at 1.475m from the reflector. What now?

Months have passed and I have come across the broken boom again. I had already planned a longer beam for my portable VHF contests (7 elements, 3m long) so I will not replace the boom.

Instead I simulated what would happen if I shortened the 5el to 4el with MMANA-GAL. The result is encouraging because without changing element lengths I can:

• install the 3rd director as 2nd director at 1.465m from the reflector
• have about 7.7dBi gain and 15dB F/B (not the best)
• keep a good match to the original 28 ohm
  

The original 2nd director remains unused, or could be used as 1st director to see if in the real world it provides any improvement (in SWR, gain, F/B, whatever).

Not bad! Well, this operation moves the center of gravity a bit behind, so I have to re-position the boom-to-mast adapter or add a little weight in front of the antenna.

I hope I can get it up and running for next Tuesday's monthly VHF activity day.

Note: the original 5 el. is DK7ZB's VHF Yagi 28 ohm with 2m boom.

Back on 30m digimodes

After few months away from HF, last night I tried again 30m PSK31. Maybe a better propagation has attracted more stations, since the waterfall was very crowded.

Might have been a coincidence, but I noticed cleaner signals than 8 months ago, and especially cleaner macros! Nobody told me about their computer and software. Only one sent me the various club codes. But ... nobody told me anything about their operating conditions, which I would have liked to know!

Thanks to the 7 guys that answered my QRP calls.

FT817 output power on battery supply: 5W or not?

There is a common misbelief that the FT817/FT817ND transceiver does not output 5W when powered with the internal 9.6V battery pack, or with an external source lower than 11V. The user's manual doesn't say that, at least the English language version.

So, does the Yaesu FT817/FT817ND output 5 Watts when powered with the internal battery pack? Does it output 5W when the "LiiI" icon is flashing?

I did the measurements and posted a video on youtube.

The setup includes a 26-30 MHz wattmeter (10W f.s.) and a dummy load, stock 1400 mAh internal battery.

I measured the output power at 5W and 2.5W level with the internal battery and external PSU. The sequence in the video is battery, external and then battery again.

The result? Even if the icon is flashing, the radio is capable of outputting 5W.

Several computers, one common file storage

I use several computers, with different operating systems too. I have personal files on all of them and never remember where they are.

If you have a similar chaos in your computers and you have easy access to broadband (ADSL or more), you might like an online folder fully integrated with your Microsoft and Linux (Ubuntu) operating system.

Search for "dropbox" in your favorite search engine. They offer 2GB of online storage, backed-up. Files will be downloaded (sync'ed) to all your installations. So you have them online and on all your computers.

If you complete few steps you can receive 4x 250MB, for a total of 3GB of storage.

You can get your first extra 250MB if you subscribe through this link (I get 250MB too).

IAC VHF, febbraio 2010

Ringrazio i 12 corrispondenti che ho avuto il piacere di lavorare ieri sera nella tornata VHF dell'IAC. DX 225km, 3 square, media di circa 100km/QSO. Questa e' l'antenna utilizzata (nella foto direzionata a Nord).

LW/MW passive loop, diagram

In case the diagram of my LW/MW passive loop could not be depicted from the description in a previous post, here is a graphical representation.

The transformer core is unknown, salvaged from some electronic equipment that needed an RF-choke to prevent RF radiation.

As a rule of thumb I would assume all those cores are good candidates for LW/MW use. I used 24 turns on the loop side and 4 turns on the 50 ohm side.