Sunday, June 04, 2017

50 Mhz transverter kit

50 Mhz had been one of those bands that I never tried, till now.

Instead of making a receive converter I went the lazy route and bought a transverter in completed kit form.

The idea for now is just to add it to a Bitx converted to 28Mhz and be used only as receiver.

This week I wired the transverter to check if working correctly, connected to the FT-707 and got some faint signals (I'm using just a bit of wire as antenna).
Today the band is more open and got one big signal from EI9FVB, after checking the call and the locator, guess what, is in the same locator as me, no wonder. Previous test, during week, I managed to receive IS0BSR/P so reception part of the kit is working.

Here's some pictures for the future box while not everything is finished, will update when complete and if using the Bitx is a viable possibility for a 50Mhz receiver/transverter.

 Transverter on top of Bitx board and the VFO on the right. I decided to buy a Bitx PCB instead o making on bare copper one since it will be faster to build.

Transverter on final location inside the box, blue wire is the temporary antenna, the black one is the IF (28Mhz) output.
For initial testing the FT-707 was used, you need to add 22Mhz, so, the receive frequency is 50.178Mhz

The 10m filter (on the right) for the Bitx input: (will also try without it and rely on the transverter filtering)
..I also made testing with the "standard" Bitx coils ( soldered on the board) for 14m, 30m and 40m case the board be reconverted (that will probably be another post). 
The 10m filter values were from here, and it's similar to many others.

...and the matching curve, no calibration on the "analyser" values, but seems to work I connected to the Yaesu input for in air 10m testing and got signals... like if that was a valid test :)

The box/front panel will be this one: still need to change VFO code's a reuse of VFO for the Telrad board from previous posts.

Have a nice week!

Sunday, May 21, 2017

Screen capture, on Linux, from Rigol DS1052E oscilloscope

Nothing fancy, just followed the code and description from here, deployed the needed libs on another Linux laptop I have, and voilà:

...a nice picture with zoom capabilities.

Had some initial problems with code in the article, had I followed the thread in the same and could had it fixed sooner. Basically the scope returns a little more data, 610 instead of 600, than expected by the Python plot function, so the following needs a change in the code:

#time = numpy.arange(-305.0/50*timescale, 305.0/50*timescale, timescale/50.0)
#time = time[0:610:1]

Where is 300 on the original is now 305 and where in the original code is 600, should be 610.

The image on the scope screen is the following:

The scope being detected as USB device:

This is running on Linux Mint with the following kernel: 4.4.0-53-generic #74-Ubuntu SMP Fri Dec 2 15:58:04 UTC 2016 i686 i686 i686 GNU/Linux

Have a nice week!

Monday, April 24, 2017

"Telrad" board to work


Just spent part of the weekend populating the "gig" with auxiliary circuits for the "Telrad" board testing, following previous posts.

Nothing special, a 9.000 Mhz BFO an LM386 audio amplifier and the power circuit, vfo is external. Not using the +12/0/-12 for supply, only +/- 9V from small batteries.

VFO is from a si5351 controled by the Arduino, signal level from the VFO is reduced to show around 100mV on the mixer carrier input pin (10)

BFO is from the Bitx and other designs directly connected to the board BFO input #11:

No provision with serial inductance or capacitance, at the moment, to "tune" the frequency.

Audio amplifier is a stock LM386 design and interestingly got some audio oscillation from the circuit that I will fix on latter experiments, probably with a RC low pass filter on the supply voltage. Connection was made at the audio output of the board and now is at the isolation transformer out.

Test signal is injected from my S9 signal generator to the front end and I do get audio ! Success...but only with injection bypassing the inboard front end filter and directly to pin 1 of the first MC1496 mixer.
Signal level injected from the signal generator even without proper measurement and calibration is probably around S4.
Audio is on the low side so more testing is needed.
I didn't managed to get LSB, only USB, have to check why (proably switching circuit) although if injecting 9Mhz directly on the LSB filter output I could be ear the signal with low level.

Another view of the first success:

I chosed 3.6Mhz since, apparently, that's around the front end filter center frequency...I start to suspect it's not, still need to bypass the filter to get audio out.
Probably in the future will remove the filter components from the board (last resource) and use a pre-amp also.
Injecting 9 Mhz on the front end is also audible as an audio tone, that's expected and is also a confirmation the board is working.

Will post more info as soon as more experiments are made.

Have a nice week!

Sunday, April 09, 2017

More filters III - "Telrad" board".

Just another update to these filters and boards as on More filters I and update II

Found the page of GW4SAE/ZL4SAE with an updated schematic of the board, no question, Will made an excellent work.

Basically just confirms the schematic from here as referenced on the previous post about this boards.

Also in regards to the filters in the board, some time ago I found the following: (From here and here)

XF-9 S 44
XF-9 S 42
XF-9 S 43

S42: bande passante=+/- 3k6 à -3db : fréquence centrale 9.000000 MHZ
S43: +/-1K55 à -3db : 8.998200 MHZ
S44: +/-1K55 à -3db : 9.001800 MHZ

Capa d'entrée et de sortie: 25 pF
Z entrée/sortie 560 ohms (mesurés)  ..."

In the mean time I started to prepare the board to make also some experiments, maybe a future receiver.

Backside of board:

Removing the extra hardware:

Have a nice week!

P.S. Just made a small jig to take on the underside the audio amp, bfo and vfo for further testing, time permits:

Sunday, April 02, 2017

S9 signal generator, another one.

This is not my first one, anyhow since the other is 1600Km away and I needed to tune a receiver, here's the "new" one:

 Allready helping tunning IF coils of a transceiver in kit form (will write more on that latter):

Here's the schematic:

It's similar to the Elecrat signal generator ( and the Norcal one.

The schematic I loosely followed is from here: KV4QB has a nice write-up on the generator.

I didn't placed the capacitor in series with the crystals and the attenuators are both in line since I'm interested on the lowest possible signal.

Construction and boxing, an house electrical junction box and some pcb made the trick:

The power clip for the 9V battery was made reusing one old battery terminal and then glued for rigidity:

Testing connected to the FT-707 it displays around S1 but since I calibrate the s-meter by ear, guess might be getting wrong results, If time permits will test with the AD8307 ...anyhow that one needs calibration also.

Here's level to s-meter table:

Have a nice week!

Thursday, March 30, 2017

Boxing the LC meter

Got one of those "cheap" LC meters from the usual online shopping site:
The unit reference as advertized is:
"LC100-A High Precision Digital inductance Capacitance L/C power Meter module"
I might add: just doesn't make toasts but better than sliced bread...

Quality of the meter is not bad and looks quite accurate, at least I measured some marked capacitors and inductors and was in the specified values/range.
The only lower construction quality part was the alligator cable that was delivered with the meter, it was not soldered, just crimped, that's been fixed already:

So far it has helped me to identify some cap's that lost marking and confirming inductors for filters.

The box used is a box for housing electrical stuf with water projection protection (not needed) and was used mainly because it's plastic, relatively cheap and I could make all the holes with a knife.

It ended up like this:

I used very short cabling for the leads so it does not influenciate much the measure.

Before every measure or changing ranges a calibration/zeroing is needed, here's the procedure:

* Inductance: Short the terminals, press the reset (red button), insert the inductor and then measure

* Capacitance: Open the terminals, press the reset (red button), insert the component and measure


Power is provided by an usb cable directly to the board. The power switch was set to always on.

Another view:

In the mean time I wrote the knobs function directly on the plastic cover since I kept forgetting.
After the multimeter this is probably the second most used test equipment here, really handy.

Have a nice day!

Thursday, February 02, 2017

More filters II

Some long time ago I bough a board with some SSB/AM filters atached, the idea was to remove and use the filters for some receiver. Upon receiving it, thought it would be nice to use the board itelf since it cointained what looks like an IF chain of a receiver. Never had the time to reverse engineering it.

The board is this one as on the original post:

Some other sellers on the "eb/seller" site are just advertizing the filters, I have another filter kit that got already in separated state from the mainboard.

Today I got an email from Szilard - HA6VSR that kindly provided links, that he found, to the diagram and description. The diagram looks like what I was expecting (even better) except I tough the AM filter was for AM, in fact is used as a first filter in chain for the 9Mhz SSB ones as per the diagram from the link bellow:

I think it will be easy to make a receiver with this, time permits...

The links, courtesy of Szilard:


Have a nice day!