Search found 112 matches

by VK2DDS
Wed Apr 16, 2014 8:52 pm
Forum: General Discussion
Topic: Brenton VK2MEV (now VK2DDS) on ABC Open
Replies: 5
Views: 618

Re: Brenton VK2MEV on ABC "Open"

I never thought it would actually get on TV when my mate recorded it! He did that video as part of a project for uni, apparently everyone in his class had to make one. I would have thought more about my answers if I'd known it would be aired nationally :p.

FWIW I'm VK2DDS now.

-Brenton, ex VK2MEV
by VK2DDS
Sun Dec 15, 2013 7:32 am
Forum: Regulatory, Licencing & Exams
Topic: AR Cover - EMR exposure
Replies: 64
Views: 2863

Re: AR Cover - EMR exposure

Near field calculation code is complete, the MATLAB/Octave code is below. Hopefully it contains enough comments that interested people can modify/experiment with the code. The results have been sanity checked (eg: far field E/H asymptotic to sqrt(u/e), impedance of free space in ohms) but the code h...
by VK2DDS
Sat Dec 14, 2013 7:36 am
Forum: Regulatory, Licencing & Exams
Topic: AR Cover - EMR exposure
Replies: 64
Views: 2863

Re: AR Cover - EMR exposure

<Results> Many thanks for the plots! It'll give me something to compare my results to. The existing tools *seem* to use the isotropic radiator model mentioned in my first post. I conjecture that this model is totally useless (ie: provides order of magnitude errors) close to the antenna. Take, for e...
by VK2DDS
Fri Dec 13, 2013 9:05 pm
Forum: Regulatory, Licencing & Exams
Topic: AR Cover - EMR exposure
Replies: 64
Views: 2863

Re: AR Cover - EMR exposure

Quick follow up to my previous post: I found the equations that describe E and H fields close to a short current segment. Integrating/numerically summing over a number of segments with an assumed dipole current distribution will allow calculation of the near field intensity. The equations were taken...
by VK2DDS
Thu Dec 12, 2013 2:00 pm
Forum: Regulatory, Licencing & Exams
Topic: AR Cover - EMR exposure
Replies: 64
Views: 2863

Re: AR Cover - EMR exposure

Assumptions? No assumptions at all.... Sitting next to an antenna that close regardless of TX frequency, shows rather basically that EMR guidlines are just not followed... Lets do some calculations/estimates then: From the photo I estimate him to be ~1m from the antenna. This is the biggest source ...
by VK2DDS
Tue Nov 12, 2013 2:41 pm
Forum: General Discussion
Topic: Is CW still worthwhile learning or re-learning?
Replies: 56
Views: 2984

Re: Is CW still worthwhile learning or re-learning?

Now, I've only been doing this 4 or 5 days now, with about 20 minutes practice or so a day but I need some advice. Do I just keep practicing at the default effective speed hoping it will come to me eventually, or should I lower it? Appreciate any advice from you CW gurus! Hi Theo, I wrote this via ...
by VK2DDS
Sat Oct 26, 2013 6:59 am
Forum: LF, MF, HF
Topic: Damping 10m Yagi Vibrations
Replies: 9
Views: 648

Re: Damping 10m Yagi Vibrations

Thanks for the help guys, I threw some rope inside the vibrating element and it did the trick!
by VK2DDS
Fri Oct 25, 2013 8:46 am
Forum: LF, MF, HF
Topic: Damping 10m Yagi Vibrations
Replies: 9
Views: 648

Re: Damping 10m Yagi Vibrations

That's the 2nd suggestion of rope I've had, looks like that'll be the first experiment. I put rope on the outside of the driven element to act as a small compression load and the reflector started to vibrate instead (at a slightly different frequency, same 3 node oscillation mode though). Owen, the ...
by VK2DDS
Fri Oct 25, 2013 5:58 am
Forum: LF, MF, HF
Topic: Damping 10m Yagi Vibrations
Replies: 9
Views: 648

Damping 10m Yagi Vibrations

Hi All, I recently constructed a homebrew 2el 10m yagi and have found that the driven element has a rather serious under-damped oscillation mode; it vibrates at about 40Hz or so: (YouTube down-samples to 25fps so you only see an alias frequency in the video) pdtPVaEQIlA Anybody got ideas for damping...
by VK2DDS
Sun May 19, 2013 9:18 am
Forum: LF, MF, HF
Topic: Noise levels
Replies: 18
Views: 1150

Re: noise levels

Newcastle close enough to Sydney? S5 50Hz buzz on 20m this morning, noise blanker takes it down to S1 static. My noise on 20m varies dramatically from S9 to S0 (typically late at night), there's probably a plasma TV nearby. Antenna is a full wave 40m delta loop strung up ~13m down to ~6m. I had the ...
by VK2DDS
Sun May 12, 2013 8:58 am
Forum: Contests, Field Days, Portable Operation, JOTA, SOTA
Topic: Trans Tasman 80/160 2013
Replies: 35
Views: 1454

Re: Trans Tasman 80/160 2013

That's a good tally - heard that Vk2AWX were up over 250 so the scores are looking pretty good.. 290 was the final tally :). We heard one station above us: VK2TQ was at 295 with half an hour to go, that was the last time we had a QSO with them. All but one of the operators who participated in activ...
by VK2DDS
Mon May 06, 2013 10:25 pm
Forum: General Discussion
Topic: Portable (Handheld) 1/4 wave Ground Plane
Replies: 10
Views: 711

Re: Portable (Handheld) 1/4 wave Ground Plane

I've had great success with half wave "flower pot" antennas: http://vk2zoi.com/articles/half-wave-flower-pot/ Haven't built one for 70cm, but 2m ones are quite easy to build and go very nicely cable tied to a backpack while bushwalking. Also built one for 6m FM (design at the bottom of that page) wh...
by VK2DDS
Thu May 02, 2013 7:12 am
Forum: FM, Repeaters, D-STAR
Topic: Complete the sentence
Replies: 34
Views: 7394

Re: Complete the sentence

Finally managed to reach repeaters (VK4RBR/VK4RZB) with my portable but my voice sounds weird (muffled?), to say the least. Strange thing was at 0130H today I couldn't reach them - and at 1551H suddenly it seemed ok. Odd, considering I changed nothing! Without knowing where you are relative to thos...
by VK2DDS
Tue Apr 30, 2013 7:19 am
Forum: PC/Mac Hardware
Topic: Echolink via Notebook
Replies: 12
Views: 4301

Re: Echolink via Notebook

...they will probably want a large amount of money to open the ports on that unit. A friend of mine (VK2VXT) has been looking into 3G dongles for an Echolink node. As it turns out it's standard practice to place 3G customers behind a NAT firewall, presumably because this is cheaper than providing a...
by VK2DDS
Mon Apr 08, 2013 11:48 pm
Forum: General Discussion
Topic: What's on your Workbench?
Replies: 615
Views: 83821

Re: What's on your Workbench?

This was my last project: 279805_10151531085356154_91903426_o.jpg It's a DSP speech processor ( discussed elsewhere on this forum ). So far I've had 3 positive reports (after setting it up with a local receiver) and one negative (setting with a random guess, no local listening). The PCB was milled b...
by VK2DDS
Sat Apr 06, 2013 8:31 am
Forum: Contests, Field Days, Portable Operation, JOTA, SOTA
Topic: Field day sites near Newcastle
Replies: 6
Views: 500

Re: Field day sites near Newcastle

Mt Allyn is probably the best spot then, Careys Peak would provide better coverage (it's about 400m higher and has a clearer view) but it's hiking access only. The Mt Allyn summit area consists of a car park area (about 15x15m, very approx) and a short (~100m) ridge which ends at a peak area about 1...
by VK2DDS
Fri Apr 05, 2013 10:23 pm
Forum: Contests, Field Days, Portable Operation, JOTA, SOTA
Topic: Field day sites near Newcastle
Replies: 6
Views: 500

Re: Field day sites near Newcastle

Hi Ben, Welcome to the area! Congratulations on not having to live in Sydney ;). What kind of field day site are you after? For VHF/UHF there are a few good coastal lookouts within Newcastle such as strzelecki lookout or Dudley/Redhead bluff. Further afield it's possible to drive to the top of Mt Al...
by VK2DDS
Thu Mar 28, 2013 8:36 pm
Forum: General Discussion
Topic: RF Burn from mobile phone
Replies: 24
Views: 1235

Re: RF Burn from mobile phone

My 2c: An RF burn will show an intensity pattern equal to that of the radiation strength around the antenna. In other words it won't show a rectangle but some form of peak spot/line with a decay around it (heavily skewed by the conductivity of your body etc). (Because Kevin did it :p) -BSc (Phys), D...
by VK2DDS
Thu Mar 28, 2013 8:15 pm
Forum: 144 & 432 MHz
Topic: 2Metre operators in the Hunter area VK2
Replies: 1
Views: 427

Re: 2Metre operators in the Hunter area VK2

Yeah, I should probably listen/cq on 144.100 more often, there's line of sight about 50km down the coast from here!

Edit: Re 5A: I didn't notice anywhere near as much difference from 5A going as I do from turning off my computer's LCD!
by VK2DDS
Fri Mar 22, 2013 6:42 pm
Forum: Arduino, Picaxe, Raspberry Pi, and variants
Topic: Raspberry Pi as WSPR transmitter
Replies: 3
Views: 3334

Re: Raspberry Pi as WSPR transmitter

That's bloody brilliant! I've got 3 floating around and hadn't thought to generate a square wave on a GPIO pin. Time to check the code... Edit: This code is configured to Tx every 2min cycle, it's easy to add a line to the C code to make it Tx randomly though. Something like this would probably do t...