Getting started on 23m EME

[VK2CBD]

Hi all,

I have been slowly getting a 3m station together for 23cm EME and would like to do some RX tests (RX at my end). My question is how best to organise this?

Does the EME community use http://www.chris.org/cgi-bin/jt65emeA or should I be looking elsewhere?

Thanks,

Brett, VK2CBD

[ZL1RS]

The N0UK logger you mention is mainly swamped by 2m JT65B EME activity. Try the http://hb9q.ch Logger Menu and register ... that is supposed to be more popular with the higher band EMEers. I just logged on and there seems to be some recent "activity" on the 1296 page ...

Good luck, Bob ZL1RS

[VK2JDS]

HB9Q's logger is the best place to start. you can always tee up a signal from some of the locals via pm here too. Phil vk4cdi is usually about , or myself. Rex vk7mo gets on sometimes.
big signals to set up skeds with include Dan HB9Q and Howard G4CCH, possibly OK1DFC if he has his 23cm feed on.

let me know when you want to test and i will be happy to help

73's from Dave vk2jds

[VK2CBD]

Bob/Dave,

thanks for the info - I'd be keen to try something this weekend. Not sure what conditions will be like though?

Is it easier to attempt to detect an unmodulated tone, or try for a JT65 contact? From my point of view I think a tone would be simpler as I have still have some learning to do on JT65...

I am seeing about 11.5dB of sun nosie with my 3m antenna and a W0LMD dual band CP patch feed + 0.5dB NF LNA. I am in the process of building a G4DDK LNA, but that won't be done for a little while yet. I am guessing I will need a reasonably large station to work with else I won't hear much?

Cheers,

Brett, VK2CBD

[VK2JDS]

Hi Brett, that sun noise rise figure is good.
you are measuring that with a program called NFM?
I will be around from now onwards to the end of the weekend and conditions are very good. the moon is easy to see and you can get americans around 1296.020 on cw at moonrise and europeans around 010/020 and 065 on digital
i think jt65c is your best bet, listen on 065-doppler shift.

a short info on doppler:
on cw a receiving station nets their echos onto the station they are hearing so their transmission fits down the cw filter of the dx station. this is all good provided you can hear you own echos.

on jt65c its different, each station transmits on 065 (or 060 etc) and the receiving station then uses wsjt to determine the doppler required to decode the dx station. so stick to 065 and tune up or down to receive. to listen near moonset for example the europeans will require little if any rit however for vk's you will need lots of offset.

when you start up wsjt9 and enter in your station information it will give the doppler for your own echo. this will be pretty close for any other vk's that might be on too. rit down to it, or use split vfos : set tx for 065 on A vfo, then use B vfo to tune around and set 'split' on your radio.

hopefully your set will be on frequency . rubidium standards or gps references are handy to rig lock

[VK2JDS]

i should add
that plate feed is fine for receive, but on transmit it requires a very high isolation relay, i fried a few preamps using good quality coax relays and 100 watts and still have the old plate feed here kicking around somewhere.. there was some arcing
best to change over to a septum when you can, you will find construction details at ok1dfc's website

for NFM (noise figure meter) go to vk1od's website and free download it. its excellent

download and install it
back off the rf gain of your receiver so the hiss is greatly reduced (like about 4 S points down)
point your dish into the sky away from the sun , avoiding trees etc
click on the 'noise lo' button
aim the dish at the sun optimising the increase in noise from the receiver
click on the 'noise hi' button
it will make a calculation of the sun noise rise for you.

the reason for backing off the rf gain is to stop the receiver agc from working as we are measuring the actual noise level from the sun as a source.

[VK2CBD]

Dave,

I am measuring sun noise with a HP8594E SA. Measuring in a 1MHz BW with a slow trace and narrow VBW. So my RX (IC910H) is not part of the measurement at the moment, but it shouldn't degrade things too much as I have plenty of gain and a reasonasble LNA ahead of it. All OK on the septum feed - actually I have one, but was having trouble finding the focus point of the dish and phase centre of the feed, so I have reverted back to the patch to simplify everything. I will try to to get the septum feed sorted soon.

I will try NFM to see whether I can repeat my results.

Interesting on the arcing - that doesn't sound good. Also on CW versus JT - I didn't realise the differences there. I will check my radio to see how far off freq it is. I have a high stab osc, but it's been a long while since I have checked it.

I'll have a listen tonight on the freqs you mentioned.

Cheers,

Brett

[VK2KRR]

I'd be careful looking at sun noise figures at the moment as the sun has been quite active and producing more noise than usual. Ive been seeing up to S9 noise on 2m and S6 to 7 on 23cm here over the past few days when aiming at the sun.

[VK2JDS]

Hi Brett, i have been on cw on 020 and listening on 065 tonight and all is quiet.
give me a ring when you want a signal

the PA batteries are charging up slowly, i have been dumping 18 amps at 24v into them all day but it will need another few days to bring them back up to good again. no sun now so the charger is off. i left the relay and bias switch turned on when i went away for a week

see if you can repeat the sun noise rise figure using the 910
use NFM and back the rf gain down so the Smeter shows s9 of bars then make the calculation.
i use a tek 2711, but best to get the ic910h to do the measurement as its the instrument you will be using for contacts.
73's Dave

[VK2JDS]

Hi Leigh, I just did another sun noise rise measurement this morning and its 15.7 dB at the moment. this is consistent with what i normally get using the big dish and G4DDK.

[VK2CBD]

Dave,
have you got time to do some tests on 23cm tonight?

I'll need the moon at least 15 degrees above the horizon, so I guess we'd need to wait until about 21:00.

Cheers,

Brett

[VK2JDS]

sounds good Brett, ring me on the telephone if you want to fine tune the times etc
0429 109622
otherwise i will be on 1296.065 + doppler on JT65C calling you every second period. make sure your clock is updated on your shack pc.

so, tune your receiver to 1296.065000 and i will workout the doppler and adjust my transmit for you. takes out another one of the variables hihi.

73's from Dave

[VK2CBD]

ok thanks Dave - all sounds good.

[VK2KRR]

Hi Dave
It was certainly quite high here the other day when I looked after the larger solar flares which increased the K index to about a 6 I think. I note that now the K index is a 1, so its come back to normal levels again.
I'll point the antennas at it again next chance I get.

[VK2JDS]

I had a random cw contact with N4PZ last eve on 1296.017, then went up to 065. Brett could hear me and also N4PZ calling cq on 017 but not decoding me
A couple of things :

Make sure the dsp is OFF in your ic910
Adjust the soundcard receive level and the slider in the bottom right corner of specJT so the 'RX noise' box on the bottom of the main screen is showing 0dB
Add an outboard DSP speaker or inline module. I use a NEIM1031

http://www.bhi-ltd.com/index.php/produc ... ayout=item
get one from here : http://www.andrewscom.com.au/site-section-01.htm
I have copied ssb off the moon with this unit in line many times. good for cw too and it allows me to more clearly hear my own echos rather than listening in the noise for them.

It was good to see 4 Australian stations in the HB9Q logger 1296 chat box.(5 if you include me) Shows the world we are active and some of the european countries think we are rare dx hihi!

[VK2CBD]

Dave,

thanks for your efforts last night. I was a great success from my point of view. You will shake your head when you hear what I have to say next however...

After we finsihed I thought some more about why signals weren't that great. The I started thinking about my W0LMD feed - my ex AO40 W0LMD feed...

Yes it would seem I had RHCP on the sky (LHCP feed), rather than LHCP on the sky.

Needless to say I'll be make some changes to my feed and trying again soon, maybe tonight.

Cheers,

Brett

[VK2JDS]

Dont be worried Brett, now you know.
Tonight i will be back on again. after 9pm or so?
the batteries are coming back up to full again after all the calling last night

did you have a look at the specJT pictures in the previous post? thats what it should look like

[VK2GOM]

This is interesting, but geared towards 13cm EME.

http://homepage.ntlworld.com/john.g4bao ... RT2010.pdf

'The Bodger's Guide to Patio Moonbounce'

73 - Rob VK2GOM / G0MOH

[VK2CBD]

125900 2 -25 2.6 -264 9 *
125900 2 5/28 VK2CBD VK2JDS QF46 1 0
130000 0 -33 6.2 -328 4
130000 2 5/28 VK2CBD VK2JDS QF46 1 0
130100 1 -26 2.7 -73 8 *
130100 2 6/29 VK2CBD VK2JDS QF46 1 0
130200 0 -33 9.0 -603 47
130200 2 6/29 VK2CBD VK2JDS QF46 1 0
130300 0 -27 2.6 -92 10
130300 2 6/30 VK2CBD VK2JDS QF46 1 0
130400 0 -33 1.8 -404 9
130400 2 6/30 VK2CBD VK2JDS QF46 1 0
130500 2 -25 2.7 -110 10 *
130500 2 7/31 VK2CBD VK2JDS QF46 1 0
130600 0 -33 1.8 447 46
130600 2 7/31 VK2CBD VK2JDS QF46 1 0
130700 1 -25 2.7 -127 11 *
130700 2 8/32 VK2CBD VK2JDS QF46 1 0
130800 0 -33 5.0 159 4
130800 2 8/32 VK2CBD VK2JDS QF46 1 0
130900 1 -27 2.7 -151 7 *
130900 2 9/33 VK2CBD VK2JDS QF46 1 0

[VK2JDS]

well its decoding me Brett, but signal levels are low.
getting the septum optimised and fitting the g4ddk should improve things

you arent too far to come for a drive and have a look here if you want to bring along the feed and lna to test etc

73's from Dave