So far you know my lab has a:
- PIC16F84 programmer
25 June 2007
PIC programmer
Here's the first post for the "equipment" category. This is the first homebrew piece of my lab that I happened to use: a PIC16F84 serial programmer to be used with WinPic by DL4YHF.
So far you know my lab has a:
So far you know my lab has a:
Restoring a 15 years old CB antenna
I still own my first (and only) mobile antenna: a CB antenna by CTE named "Dallas". It has been outside for many years and used seldomly until I dedicated it to my 10m beacon (pictures).
One day I measured it with the MFJ antenna analyzer and discovered that it showed an horrible SWR, with a best 2.5:1 at 27.5 MHz. On 28.322 it was above 3:1 and unusable anywhere else!
So I opened it up. It's very easy: unscrew the whip part and slide off the plastic cover of the coil. Surprise surprise: it used a tapped coil of 15+3 turns (also called autotransformer). There is no visual damage to the coil and continuity tests showed zero ohms: no obvious damage to be fixed.
Since I am also looking for a 6m mobile antenna, I thought I might reuse the support for the base loading coil. Let's first try a quick fix for 10/11m: interrupt the tapped coil so that the antenna becomes a base loaded vertical:
A second run on the antenna analyzer made me smile: the resonance now moved to 28.8 MHz with 1.1:1 SWR after the 3m of RG58 coax. The antenna on the balcony fence is usable on the whole 10m band! :-)
What's next: measuring it on the car. Bandwidth might broaden a bit.
One day I measured it with the MFJ antenna analyzer and discovered that it showed an horrible SWR, with a best 2.5:1 at 27.5 MHz. On 28.322 it was above 3:1 and unusable anywhere else!
So I opened it up. It's very easy: unscrew the whip part and slide off the plastic cover of the coil. Surprise surprise: it used a tapped coil of 15+3 turns (also called autotransformer). There is no visual damage to the coil and continuity tests showed zero ohms: no obvious damage to be fixed.
Since I am also looking for a 6m mobile antenna, I thought I might reuse the support for the base loading coil. Let's first try a quick fix for 10/11m: interrupt the tapped coil so that the antenna becomes a base loaded vertical:
A second run on the antenna analyzer made me smile: the resonance now moved to 28.8 MHz with 1.1:1 SWR after the 3m of RG58 coax. The antenna on the balcony fence is usable on the whole 10m band! :-)
What's next: measuring it on the car. Bandwidth might broaden a bit.
20 June 2007
IK1ZYW/5
This is not really a homebrewing post, but I finally managed to get to use the stuff I built.
During a holiday in Toscana I could spare some 30-minute packs for radio activities. The shack was in the bungalow bedroom, on the bed:
FT-817 on the pillow, with earphones and homebrew CW paddle. Pencil and paper log, mobilephone as a watch. Hanging on the window a homebrew LC-tuner (my version of "ALT") with 5 switchable series inductances (0.5, 1, 2, 4, 8 uH) and 200pF swappable IN-OUT across capacitor.
The radiator was made of 12m of wire held vertical with a 9m fiberglass fishing pole, then 3 random counterpoises were laid on the ground:
This antenna tuned on all bands between 80 and 6 metres, including WARC. I had contacts on 80, 40, 20, 10 and 6, including some 2xQRP on 20 and 40m.
After the first few days I switched to battery power because the old laptop power supply was generating too much RF noise. Power has been 2.5W or less.
The 2600mAh pack gave about 3 hours of CW operations at 2.5W, with a 40/60 TX/RX rate.
During a holiday in Toscana I could spare some 30-minute packs for radio activities. The shack was in the bungalow bedroom, on the bed:
FT-817 on the pillow, with earphones and homebrew CW paddle. Pencil and paper log, mobilephone as a watch. Hanging on the window a homebrew LC-tuner (my version of "ALT") with 5 switchable series inductances (0.5, 1, 2, 4, 8 uH) and 200pF swappable IN-OUT across capacitor.
The radiator was made of 12m of wire held vertical with a 9m fiberglass fishing pole, then 3 random counterpoises were laid on the ground:
This antenna tuned on all bands between 80 and 6 metres, including WARC. I had contacts on 80, 40, 20, 10 and 6, including some 2xQRP on 20 and 40m.
After the first few days I switched to battery power because the old laptop power supply was generating too much RF noise. Power has been 2.5W or less.
The 2600mAh pack gave about 3 hours of CW operations at 2.5W, with a 40/60 TX/RX rate.
QSL: IW3FQZ/B
I received this beacon while /M on A4 Italian highway, driving at 120-130 km/h.
This was a ground wave/direct wave reception.
This was a ground wave/direct wave reception.
31 May 2007
Magmount base apocalypse
D@mn d@mn d@mn!
After 15 years I bought a new magnetic base to use on my car. At the local shop (yeah, we still have a CB/HAM store!) I got a thing called BM-180-PL, 100% China Export.
The magnet is large but I have the feeling it is not so strong.
At the first usage the nut holding the SO-239 in place lost its thread and the center conductor from the RG58 cable detached (it was even a cold solder joint!) . Forensic analysis showed that the nut was made of aluminium. No wonder...
After my fix the rubber protection does not stay in place anymore.
Today I tried to detach my old "President Dallas" antenna from the base but... antenna and SO-239 were turing together!!!!!! D@mn d@mn d@mn!
After 15 years I bought a new magnetic base to use on my car. At the local shop (yeah, we still have a CB/HAM store!) I got a thing called BM-180-PL, 100% China Export.
The magnet is large but I have the feeling it is not so strong.
At the first usage the nut holding the SO-239 in place lost its thread and the center conductor from the RG58 cable detached (it was even a cold solder joint!) . Forensic analysis showed that the nut was made of aluminium. No wonder...
After my fix the rubber protection does not stay in place anymore.
Today I tried to detach my old "President Dallas" antenna from the base but... antenna and SO-239 were turing together!!!!!! D@mn d@mn d@mn!
28 May 2007
Boom to mast
I could finally work out a way to plug the 5 element on a fishing rod.
My mast will be a telescopic fiberglass fishing rod. I need a way to attach the boom that does not compress the rod structure: no screws and no holes!
So I sled the "4m telescopocket" fishing rod into a segment of 25mm PVC pipe: it stops somewhere at about 2.3m from rod bottom. Enough for a VHF yagi! So I found this way of attaching the PVC pipe to the boom:
I might also add a small 3mm screw in the intermediate holes to reinforce the whole assembly.
Please do not tighten nuts too much otherwise the PVC pipe bends inwards!
My mast will be a telescopic fiberglass fishing rod. I need a way to attach the boom that does not compress the rod structure: no screws and no holes!
So I sled the "4m telescopocket" fishing rod into a segment of 25mm PVC pipe: it stops somewhere at about 2.3m from rod bottom. Enough for a VHF yagi! So I found this way of attaching the PVC pipe to the boom:
I might also add a small 3mm screw in the intermediate holes to reinforce the whole assembly.
Please do not tighten nuts too much otherwise the PVC pipe bends inwards!
22 May 2007
Lab in the kitchen
You don't need a whole room to have a lab, the kitchen table can be very helpful for some night building sessions!
Don't forget to clean it up for next morning breakfast!
Don't forget to clean it up for next morning breakfast!
17 May 2007
How does a DRM converter looks like
This is what I built for an SWL for his R-75.
From left to right: IF cable (top), 12 kHz cable (bottom), converter, 9V clip, on-off switch.
From left to right: IF cable (top), 12 kHz cable (bottom), converter, 9V clip, on-off switch.
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