Thursday, 5 October 2017

New Driven Element

I've changed the driven element of my DK7ZB to the DG7YBN (K6STI) style. This has the advantage of a 50 ohm direct feed eleminating the need for the 50-28 Ohm DK7ZB match. I've had problems water proofing the old match and not been able to source decent 75 Ohm coax anyway.
VSWR is very low and as far as I'm able to tell there is no loss of gain. Proof of the pudding will be in the eating.  EME contest this weekend so if I can make a few contacts I'll be happy if not I might have to reinstall the old DE.
The DG7YBN driven element

Update 15th October 2017

First EME contact with the new driven element

And it seems to work



Saturday, 16 September 2017

FT8 on Six Metres

Started the Sporadic E season this year using JT65A again, never had any idea that FT8 would be coming along.  Just happened across it somehow, really can't remember.  Downloaded WSJT-8 and joined in the fun.
FT8 really comes into it's own on Six where short lived openings would probably be missed with JT65.  FT8 apparently looses some sensitivity compared to JT65 but the great advantage of quick fire contacts more than makes up for that.  Auto sequencing helps to speed things along. Wasn't too sure about that at first but soon subscribed as the fifteen second over can leave you floundering unless you are very quick and I wasn't.
If I'm around the shack but not able to operate I often just leave things running to see what is about sometimes with surprising results mostly capturing random calls form the continent when otherwise the band is dead.

PET HATE: stations sending RR73

Here's a nicely flowing FT8 QSO on 50MHz

Nicely flowing FT8 QSO
For FT8 I'm using a homebrew Six & Four Metre transciever, HB9CV antenna and 100 Watts.

Thursday, 17 August 2017

RF interference noise from garden solar lights

Below is a video of the RF noise generated by three strings of 20 LED solar garden lights located in a neighbours garden. Cheap Chinese imports. The noise is S9 on Two Metres and my antenna is 200 feet away.  The interference is strong enough to be heard no matter where I point my beam including at the Moon.  Of course there is no noise during daylight, one small mercy I suppose!  70MHz & 50MHz are also affected, not sure about HF as I'm not really active there but I'll check soon.



Search using "Simple solar circuits" should give results that may help explain why they generate so much interference.

Here is a screen shot of 50MHz, the peaks of noise are sharper than on 144MHz and drift downward in frequency.

The RF noise drifting across Six Metres
I've purchased some clamp on ferrite suppressors. I will speak to my neighbours and hope they will be willing to fit them but I'm not confident that even if they are fitted the noise will be suppressed to the extent that it's not detectable. Even very low level noise will be a problem with EME.

UPDATE; The noise is also on HF 

Small peaks of noise are detectable on HF but appear fairly static and so if outside of a band they may not a problem. I'll update with a screenshot soon.

Sunday, 16 July 2017

WSPR spots while using dummy load

QRP-LABS U3 1Watt into dummy load
Having destroyed the BS170 FET in my QRP LABS U3 I decided to press a small driver amp I'd made into service instead of replacing it.  Wasn't sure what power out I would get and was pleasantly surprised with the easy 1 Watt it produced driven directly by the  Si5351A synthesiser.  The driver was running in class A so no easy way to turn the power out down but nevertheless I decided to soak test and left the U3 running into a dummy load for several hours.  Really don't know why I decided to check WSPRnet for spots and was amazed when several came back.  As you can see in the photo nothing was screened. Perhaps there is a warning there for the next time I start whistling into a dummy load
The spots I received

Sunday, 4 June 2017

Pskreporter and DX

Don't you just love PSKreporter, tells you all the DX you've missed while your out and about. Here's what my radio received today on Six. Best of the bunch A6VQ TY2AC AB1NJ. Oh well, most likely wouldn't have worked them anyway.

Friday, 23 December 2016

Successful EME contacts

Massive EME array?  8 element DK7ZB
 Success

After several weeks of trying I finally got lucky and had two QSOs via EME.  Below are several screen shots from the contacts. The only thing that was different this time was the antenna. I used my 8 element DK7ZB instead of the thirty year old 9 element Tonna.  The Tonna is showing signs of it's age and I'm wondering if the corrosion is affecting it's gain.

Equipment

Modified Kenwood TM255E (SI570 LO, IF tap)
Homebrew SDR tuned to TM255E IF
Homebrew 300 Watt amp (Freescale MRFE6VP6300 mosfet)
8 element DK7ZB  (gain 12 dBd)
Software;
WSJT-X v1.7.0-rc2
PowerSDR-IQ


So I'm pretty happy with that and looking forward to more contacts.

Transmitting RO
Completed QSO
The second contact was an answer to my CQ, pretty suprised I can say
Second contact
And a card