Meter repair

Some years ago I grabbed my tent and went to Germany to the ham radio exhibition. The idea was to leave the tent and on the spare space bring a lot of junk.
I did managed to bring the tent and the junk... although at the Swiss airport (I went via Zurich) control was difficult to put everything inside after removing the tent to explain what was that on the x-ray..... they weren't interested in the wires, valves, meters, etc... oh well.
Unfortunately 2 of the meter I bough were damaged... can't trust some sellers.. today I did managed to repair one, some soldering's and voila... some one had already tried but without success since some nut's were inside wrapped in paper. The other metter was a Russiam metter and the moving coil was in open state...so almost impossible to repair, will keep the magnet.



The idea was to use the meter in my future rf power meter but honestly it is to big for finding a nice box. Will be used in some other project. This meter must had come from a "m Ohm" meter, don't need one for the moment but let me think that it must had used a Wheatstone bridge or something similer for measuring.

I have one 150uA meter from the "Westinghouse Electric Company" and probably will be the one to use, after all "Mr Westinghouse" was a defendant of the "Alternate Current" although for some more "dBm" that I intent to measure....

HF radio (4)

...The first sound.... not quiet what I was expecting but already some reception. The radio is a little deaf (no rf preamp and no rf input filter at this moment).
Made some more tests after this video, changed the first if preamp schematic a little bit but not much improvement, still have to check levels on sbl-1 mixers and verify all the if gain part of the cristal filter and mc1350. Basically at this point is copying equivalent to S2/3 on a commercial normal transceiver... I want a little more, also I already verified that the lower the noise the better to distribute the gain so will separate all the oscillators and different modules with some pieces od PCB.




Here's is another video at 20m band. Note that I changed the cristal filter relay in the middle of the board for a smaller one.

HF radio (3)

Still "fighting" to put the DDS programing software accessing the parallel port under "dosemu", will try now to boot DOS native...if I can find a diskete....

--Adendum--- Found a diskette with DOS, saved dds software on it, changed to another computer, changed parallel port to standard, messed with the cables... and voilá! Programed with a fresh 9Mhz "IF" more or less some little herts...I am happy -- end adendum----

Meanwile made a new "rf test probe", smaller with a less drop diode... now I have more 0.1v on my measurings. Previous diode has a drop of around 0.40 this one has 0.30 more or less... but still I have to calibrate the dam thing. I measured my DVM internal impedance.... it almos reaches the 30MOhm... wich lead me to doubt on the metod used... so I made the probe assuming the impedance was 11MOhm.
You can see in greater detail the original design: http://www.io.com/~n5fc/rfprobe2.htm












Meanwhile I had to move the shack power supply near the computer so I can program de DDS and found out that actually the power supply wasn't a laptop power supply inside a box,....I was almost sure it was..., after all it was a conventional power supply with an 7812... the other output is a varialbe LM317 type, no wonder that sometimes it shuts down with lot's of boards beeing connect.... oh well it was puttede in place an worked for so many years that I forgot completly.... the box is of "Chivas Regal" brand.... will rebuild in one of this days. The paper inside is the schematic... in case I forgot what was done....It was the case!

HF radio (2)

Now that I connected the DDS3 vfo...I just found that 7 years without use made it to lost the registers.
It was bough in 2002 and since then it was only connect 2 or 3 times so it's natural this happened... the problem is the kit is no longer sold and the software came on a 3 1/4 diskette. I was lucky, managed to read the contents (Linux command "mcopy a: .") and saved the programing software to a new disk.... but there is another problem, the software runs in DOS, I don't use DOS for some 12 years and I don't use the other operating system that supports reading some DOS applications.
Linux has "dosemu" a dos emulator. I can now run the software but still didn't tryed to programe the equipment. DOS is not exactly the "shell" ins fact is "freedos".

The vfo for now is runing with an IF of 14 Mhz, it came programed when bough with an 9Mhz IF... anyhow made some tests with vfo on 17.5Mhz and my dip metter on 8.5Mhz (8421Mhz exactly)...there are some 79Khz diference I can't yet explain for my 9Mhz IF (17.5-9=8.5 != 8.421).
Almost for shure something is working in the radio since the audio is only when the osciltor is close to the wire conneced to the sbl-1 first mixer input, I am not so positive regarding the levels on the mixers... previous experiencies show'd me that big signals always are received, problem is the smal signals... I need to make an acurate power meter!!! Does anyone has a spare AD8307 that can send me? For a reasonable price of course :)




A photo of the building process.... the first mixer, the if preamp coil, pre-filter coil, relay for cristal filter switch and 9Mhz cristal filter.

HF transceiver (1)

I am building an HF radio....It's my third atempt! I built (soldered) the "Speaky" but never put it to use, built some modules years ago but never finished them, so it's time now to make one to put on the shack.

I am using mostly parts from the schematic at: www.arrl.org/tis/info/pdf/8912018.pdf - (arrl 14 Mhz transceiver) but converted to multiband.
The vfo part will be a DDS3 from Hands Electronics and the bandpass filters from "Gqrp" design using Toko coils. VFO amp (if neded) will be the one from "Analog Devices" application note AN-557 (a simple 2n3866 amp).

I built the IF strip and it looks that is working nice. I am now testing an BFO cristal switcher so I can have LSB and USB. For now the LSB cristal is just 140Hz away from the correct frequency (8.9995)

In the video the rf generator is around 40cm from the 9Mhz if input. I still have no rf front end done except the first mixer.




There are however some "error's" I found on the schematic:

- On the second sbl-1 (connected to the bfo oscilator) the IF pins are switched , replace 3 and 4 by 5 and 6 and vice versa.
- The caps on the BFO oscillator first transistor should be 47 and not 470, probably something around 33 should work also.
- T6 ref. doesn't have the number of turns for the secondary, I am using 2 for the moment (just testing), on my "not calibrated" power meter gives 0.2v (=~ 1dbm) so I will increase later one.
- I replaced the NEC99532 transistor by an 2N3866, still have to test if it's ok.

Some metal work.

This will be the box of my new/old project. An all band / all sort of controls/ ultra high performance (basically similar to an ne602...) hf transceiver... I have for some years an dds-3 kit so it will be used for vfo, also have an 9Mhz filter that I bough some years ago as the bfo cristals. The bandpass filter design is somewere on this blog.
First mixer will be an sbl-1 and second probably the ne602 or another sbl-1. The design is a mix of several designs and will be used the ones that work beter.

B box

First: I have no financial interests in this brand.
Second: Enclosures for experiments are getting everyday more expensive.

Went for lunch at a little restaurant and found they have some nice napkin holder....
This will be the perfect box for some small circuit although it's plastic on one of the covers and have small holes for the napkins it will suit fine.





































Now they have one less.... have to go there again :)

p.s.: the box and the napkins were offered case you were thinking different!