Screen shot of my first ever JT65HF contact!

I was shocked to see that my last blog post was almost a month ago! I have been on the radio on and off but the season has been very busy with work and then Christmas as well. I was doing some blog reading on the weekend and the Digi modes were being talked about again. In the past I have tried and tried but frustration settles in and I give up and move back to CW.  This time around I took more time and looked into the operation the JT65HF program. I do have wsjtx on my PC as well but it seemed to me that JT65HF was just a bit more basic for me and would at least get me going. The rig control I am using is DXlabs and as was said the digi software is JT65HF and Signalink usb sound card. I adjusted my output power on the K3 to 5 watts to see what would happen. I saw K0TPP calling CQ and I answered him and had my first JT65HF contact. I did not have anymore time for other contacts as other things had to be done around the house. BUT......this week I am hoping to some DX contacts.
Mike Weir, VE9KK, is a regular contributor to AmateurRadio.com and writes from New Brunswick, Canada. Contact him at [email protected].

Courtesy: http://www.ledsmagazine.com

Once again, from Jan...

"Visible LEDs and optics: Some of my favourites include the LZ1 and LZ4 series from LedEngin used with matching spot lenses, or thick condenser lenses from old visual projectors. Also various Golden Dragon varieties with matching small plastic spot lenses. Average beam divergence with either configuration is about +-4 degrees. (Happy to provide detailed parts numbers.)

Infrared LEDs: Here we have a some good products from Vishay (TSHG series), with narrow beam (some go down to +-2 degrees) in the standard 5mm packages and max current of 100mA.



They can make nice pencil-beam arrays in combined series/parallel with 200 or more LEDS and no optics required, at less than 40c per LED. Lots of soldering though :). For the 950nm range (not extensively tested yet) the Vishay TSAL range of LEDs will do nicely.

LED drivers: I found a very neat IC to PWM-drive the LEDs at up to 1A - the CAT4101 from ON Semiconductors.






Usually have two in parallel for a peak of 2A at 50% duty cycle, giving me 1A average to drive the LED string.

At the reciving end I am now using a preamp loosely based on Clint's no-feedback design with some hum filtering and other post minor post-processing feeding to an audio amp, or to SpectrumLab."
"...tonight I am trying to compare 830nm against 940nm on a 600m short NLOS path. For this, I have just built a small TX with two "naked" LEDs - TSAL6100 (940nm) and TSHG8200 (830nm). Both have identical shapes of their radiation patterns with +-10 degrees. Each mounted inside of a square cross-section black cardboard tube side by side to ultimately give them a very uniform square beam of approx +-4 degrees. Each driven with 440Hz square wave at 100mA with unique morse identifier for each.

There is a third visible LED as well with its own cardboard collimator and morse ID, to serve as aiming tool and a kind of reference.

The purpose is to see whether 940nm would offer additional advantages in NLOS situations, due perhaps to better/different reflection, scatter, refraction or whatever physical processes might be involved.
An additional advantage might be removing my setup further away from visible light pollution. With the growing popularity of LED lighting in both household and the industry we are having a chance of less and less infrared pollution from traditional incandescent or similar sources - and making light comms more practical in urban environments - all with a simple IR filter at the receiving end.


Tonight's tests were not as productive as anticipated, but somewhat educational nevertheless. First of all the receiving location I picked on the map suffered from severe QRM from sodium street lights. I picked strongly all my "big" IR transmitters, but the visible and the "naked" ones were lost in the QRM, if present at all. I returned home, pointed the 150mW TX into nearby bushland and went for a walk. The red light reception vanished immediately after loosing sight of TX, followed quickly by the 940nm with the 830nm persisting the longest up to perhaps 100m - with the beam fired parallel to ground from upper storey into the crowns of the trees. Reception required pointing the receiver slightly up, intersecting the TX beam somewhere in the tree branches.

Briefly - I confirmed what I already knew: - IR is far superior to visible for NLOS work - indeed visible light is of no use.
- Low elevations and scatter from ground objects is superior to high beam elevations.

A new observation (that I would like to confirm) is that 900+nm is not worth bothering about. It is known that 950nm suffers from greater scatter in atmospheric particles than 850, but this proved to be more of a hindrance than help in NLOS work.
Another practical observation is that the 950nm version of the common SFH213 photodiode (SFH213-FA) works very well in receiving 850nm whilst filtering out lots of the visible pollution (well, perhaps except the sodium lamps!).
I started tonight's session before sunset and got very good NLOS reception of my large IR TXs - in what could be described as quite a bright twilight. (I carry two plug-in front-end modules each with one of the two photodiodes and the input FET.)
Another holiday project - a pocket-sized 10W TX! I found new IR LEDs - SFH4783 - rated at 2W, barely 1.65V of Vf, and intrinsically narrow angle of +-10 degrees. This means no optics, and up to seven of them in series on a small heatsink can be run from a 12V SLA battery.



Osram SFH4783

This reminds me of yet another observation - out of my several large 850nm TXs the best performers are the naked narrow-angle multiple LED arrays - and the one containing 3 high power broad-beam LEDs with spot optics performing the worst. Well the lenses are designed for visible LEDs and I have no guarantee that the material refraction angles and loses are acceptable in the IR range... 

 Returning to Steve's questions and our general discourse:

..is it (the RX) fairly small and portable...and lensless?   (cont'd)...

Steve McDonald, VE7SL, is a regular contributor to AmateurRadio.com and writes from British Columbia, Canada. Contact him at [email protected].

 

So Christmas has left us again. this time I’ll be glad to see the back of it after being and bit part player in the events in George Square, Glasgow just before Christmas and spending most of the subsequent days either laid up in bed or coughing and spluttering my way round the place.

On a lighter note the days between Christmas and New Year led themselves nicely to The RSGB Christmas Cumulative VHF series. A Contest run between the 26th and 29th December that gets me out of the house and either into the wilds of Cumbria at this time of year, or as it happened yesterday one of the clearest, crispest days we’ve had in a long time.

The contest is only a couple of hours long and the choice of band(s) is up to you. I thought it would be a good opportunity to take my dual band 2m and 70cm antenna that I got from Nuxcom in the summer. The antenna is a tad fiddly to construct in the field as the elements wander with the slightest touch but the lack of wind helped there.

The rig was the usual FT-857 that I have had on loan from the club for a while now that gives me my choice of 10w out on the VHF bands.

The map above shows my results. ODX was 450 miles to G7RAU, which equals my best to date. Other bigger stations will have undoubtedly made more miles but it’s not all about the DX. Hopefully I will get the chance to get out and about on the UKAC evenings as well as the back end of the year was a bit of a non event for me. Here’s an obligatory view form the ‘shack’ and dual band antenna (Here’s a link to the original site for the antenna)

Alex Hill, G7KSE, is a regular contributor to AmateurRadio.com and writes from Cumbria, UK. Contact him at [email protected].

Tim Kirby, G4VXE, is a regular contributor to AmateurRadio.com and writes from Oxfordshire, England. Contact him at [email protected].

Tim Kirby, G4VXE, is a regular contributor to AmateurRadio.com and writes from Oxfordshire, England. Contact him at [email protected].

I have always been a big fan of moving coil multimeters, don't get me wrong the digital DMM is great. But there is something about an old fashioned moving coil meter I have always liked, a bit like the boy or grew up to be a man and still loves steam engines I suppose?


Christmas brought me a couple of envelopes with some money and I was busy browsing late last night, temptation got the better of me:



The MF500B is a full sized bench multimeter (plenty of images available on the web):

 

Steve, G1KQH, is a regular contributor to AmateurRadio.com and writes from England. Contact him at [email protected].

Some recent component finds I have on order for myself, which you may find useful for your own Amateur projects all prices seem very reasonable:


10 pieces of copper clad board useful for building your QRP projects on, size 10cm x 15cm:


http://www.banggood.com/10Pcs-1_5MM-CCL-1015-FR4-Glass-Fiber-Board-PCB-Circuit-Board-p-962233.html


2200 uF 16V electrolytic capacitor x 50 pieces:
Ideal for some decent smoothing on your project supply rails: 

http://www.banggood.com/16V-2200UF-Power-Supply-Board-High-Frequency-Electrolytic-Capacitor-p-962535.html

Steve, G1KQH, is a regular contributor to AmateurRadio.com and writes from England. Contact him at [email protected].