What is the smallest dish for serious 23cm CW EME operation?

Source: http://list-serv.davidv.net/pipermail/moon-net_list-serv.davidv.net/2008-September/  edited by OK1TEH

Od: Oene <pa3cwn@tele2.nl>
Komu: Moon <moon@moonbounce.info> , Moonnet <moon-net@list-serv.davidv.net>
Předmět: [Moon] 2.40m dish
Datum: 26.9. 2008, 08:45

Hello All,

I want to join Phil FR5DN in his question about the needs to become active on 23 cm EME. In my case I have totally NO experience with 23 cm and it's behaviour, besides working a couple of hours in a contest once as guest operator. I am more and more thinking about 23cm lately, as it seems THE band where a lot of activity is , according to the latest contest results.

What is i.e. minimal needed for CW EME on a regular base? I mean to work the average stations active on 23 cm. Is a 2.40 m dish and 150 W enough to do the job or is that too marginal ?

And what about qrm on 23 cm ? I can imagine that with a larger dish the band is much more cleaner as with a short yagi. But is qrm from the neighbourhood as much as actual as on 144 MHz ? In my case the qrm I pickup on 144 MHz is very much and vice versa; On a regular base have the neighbourhood at my doorstep complaining about TVI, LFI etc. All the nowadays equipment with oscillators generate a lot of harmonics etc. presented as big qrm especially at the start of the 144 MHz band, but is this also the case on 23 cm ? Or are those signals already soo weakened compared with 144 MHz that it is almost no issue ?

I have no equipment and have to start from zero on this band, so think there is also a lot to learn: what is the best solution a combi rig or transverter and hf trx ?

Maybe there is a good starters guide for 23 cm , because the answer from Guenter DL4MAE gave new question- marks at my side with his f/D answer and showed me that I have to study a lot before making these step. I have the time so do not have to be qrv next week and even like to build things myself, though this very high frequencies require other skills and equipment as I am used to !

You see already many questions and it is just the beginning !
Please respond to this topic in general to the mailing list rather than to me private, so others can benefit too from this. Shared knowledge is fun !

Thanks in advance and for all a very good weekend

73 Oene

Od: Edward Cole <kl7uw@acsalaska.net>
Komu: Moon-Net <moon-net@list-serv.davidv.net>
Předmět: [Moon-net] Fwd: Re: 2.40m dish
Datum: 26.9. 2008, 09:45


I am just putting together my 23cm eme station this fall. I have a 4.9m aluminum skin dish which is medium size for this band. Generally, 3m and 150w is minimum recommendation, though some do operate with a 2.4m dish. I have a 2.4m fiberglass ku-band dish that will be used for 3cm eme in a year or so.

I am building a 300w sspa kit from W6PQL that cost me $867 USD. Nice part is it is no-tune and can be mounted on the dish back so avoiding long runs of very large hardline. I will run 40w in the shack thru 30m of 1/2-inch hardline to provide 20w drive needed at PA. Only needs 28-vdc. There is no local 23cm activity here in Alaska so that is not a problem nor is RFI at this freq. The signals are down by -15 to -20 dB at the dish edge so with a 2.5 degree beamwidth I will have to point directly at neighbor for any significant RF to hit them. Gain is 34.9 dB, theoretically. For a 3m dish gain is 30 dB.

A transverter is the way to go. You can use a 28-MHz IF but 144 or 432 is better for easier filtering of image and harmonics. DB6NT makes great stuff. I am using a DEMI xvtr 144/1296 and 6w driver amp to 60w first amp (all in the shack). I have a two-stage WD5AGO preamp with 0.30 dB noise figure and 31 dB gain. I built one of the OK1DFC septum feeds.

I agree that 1296 is probably the second most popular eme band to 2m and I understand that it is much quieter. I am going to continue QRV on 2m but will spend time on 23cm, and later 9cm and 3cm. I think WiFi interference on 13cm will make it a tough band so not planning on that. No plans for 6cm eme at this time but that might change once the 4.9m dish is up!

I'm not an expert, just a good student ;-)


Od: SM6CKU <ben@parabolic.se>
Komu: freetalk moonnet <moon@moonbounce.info>
Předmět: [Moon] I repeat on reflector
Datum: 26.9. 2008, 09:51

Good morning Oene
In my opinion a 3m dish with 150 watts will do what you said. Have a look at SM5LE on http://web.telia.com/~u14901544/ and compare. He is using a 2,2m dish and 500 watts. Earlier he had some 250 watts and that was marginal to work smaller stations.
73 de Ben, SM6CKU

Od: SM5LE <sm5le@telia.com>
Komu: Moonbounce <moon@moonbounce.info> , MOON_NET <moon-net@list-serv.davidv.net>
Předmět: [Moon] resending answer to Phil FR5DN
Datum: 26.9. 2008, 10:38 - před 4 dny

Here is what I did send to Phil as "direct replies". (Steve you are right ... )

Hi Phil
Yes I think it is "worth the effort". I have 2.2 m dish and wrkd 74 stns on CW and 30 on JT65c (digital mode). It is offcorse dephending on other things also , power , LNA etc. I have wrkd with 250W and homemade 0.35 dB LNA. (from last week now 500W) I did expand a 1.8m (SM6CKU "tropo-dish" f/d 0.4) dish , to 2.2m (ending up at f/d 0.34) for adapt to OK1DFC septum feed.
Also I am very much EME QRV and that also help for good results ( I am retired - Hi) Go for 23cm first , it is fun (have QRV only for two yers now). My homepage: http://web.telia.com/~u14901544/#SM5LE%20wrkd%20inits and pics here : http://web.telia.com/~u14901546/home_page_no_3.htm

73 and G.L. Sven SM5LE

... and if you are an Africa continent , you will be very popular for WAC etc. !!! :-) /Sven

Od: SAM JEWELL <jewell@btinternet.com>
Komu: Moon <moon@moonbounce.info> , Moonnet <moon-net@list-serv.davidv.net>
Předmět: Re: [Moon] [Moon-net] 2.40m dish
Datum: 26.9. 2008, 11:28

Oene, et al
I have a 'large' dish compared with Sven, in that I use a 2.3m KTI TVRO dish. With this I use an OK1DFC septum polariser feed on both 23cm and 13cm. Both of these were kitted by G4HUP. I don't have a choke ring on either feed (yet>>>>)

On 9cm I have used a converted integrated C band LNB with modified Chaparel feed and linear polarisation. I have been amazed at just how easy it is to hear so many stations on each of the three bands with this size of dish. On 23cm I have worked 35 stations with 200w in the shack, about 150W at the feed. Of these 35 about 10 were on JT65 only.

On 13cm I have worked just two station, but this with a very much sub-optimal feed position, 50W in the shack, but a reasonable LNA (HI!). 9cm is still receive only.

A few months ago I discovered that I had previously positioned my feeds back beyond the focus by a few cm. I correctedthat and since then I have improved sun noise on both 23 and 13cm by a noticeable amount. Maybe now when I add choke rings they will have a positive benefit and not the effects noticed previously?

Last weekend I resurrected my 13cm system, on receive, and copied around 20 stations in the few hours of moon time I had available (I'm not a night person!). I am currently modifying my polar mount to give more moon time. The new 13cm SSPA is almost ready to go.

The purpose of this posting is to encourage anyone who is thinking of using a small dish to go ahead. Whatever size dish you have, it's never big enough anyway! Small dishes can work well, even on 23cm, and it will get you started....and most important.....thinking about system improvements.

If I did more operating and spent less time building my initial count on 23cm and 13cm would both me much larger, I think!

73 de Sam G4DDK

Od: peter blair <g3ltf@btinternet.com>
Komu: Oene <pa3cwn@tele2.nl> , Moon <moon@moonbounce.info> , Moonnet <moon-net@list-serv.davidv.net>
Předmět: Re: [Moon] [Moon-net] 2.40m dish
Datum: 26.9. 2008, 11:38

Oene, I endorse Ben SM6CKU 's input. SM5LE does an excellent job with his 2.2m dish and with his 250W was easily workable on CW by well establised 5m dish stations. There are quite a lot, I'll guess at 20, of big ( 8m dish and¨above) stations about on 23cm so if you put a basic 2.4m station together you will be able to work these quite easily. Then you will need to start to optimise your system, Basically Experimenting....carefully measureing sun noise, gradually eliminating losses, optimising feed position, trying different feed types, different LNAs, improving the pointing accuracy, and so on. Thats what Sven ( and others) have done. Fortunately there is now plenty of material about on the internet on how to do that, the W1GHZ on line antenna book for example Http://www.w1ghz.org/antbook/contents.htm and websites like Sven's where he descibes blow by blow what he did. And there are lots of people here on the reflectors who can help with advice. There is also the issue of aquiring operating technique and skill. Knowing where and when to call CQ, dealing with the libration fading etc. This just takes time to learn, just like when you start on any new band. One thing that the small stations do have going for them now is the increasing use of SDRs with a waterfall display which alerts the larger station to the presence of a possible QSO. 23cm is a great eme band with lots of activity and very few problems with QRM from other services and birdies which are becoming a problem on some other bands.

GL 73 Peter G3LTF

Od: Sergei rw3bp <rw3bp@co.ru>
Komu: moon-net@list-serv.davidv.net
Kopie: moon@moonbounce.info
Předmět: Re: [Moon-net] 2.40m dish
Datum: 26.9. 2008, 13:40

Hello all,

Small 2.4m dish is a limit I can have on the roof of 18 floor building This is because of conflict with neighbours and local authorities few years ago. So I am forced to get maximum from my small dish. On 23cm it is partially expanded by mesh up to 2.8m. Best result was 52 QSO in ARRL contest 2007. On 13cm last week-end ARRL contest I only tested some improvements in my station. Only 9 QSOs but with good reports. Easy QSO with OM/OK1DFC. It was not expanded 2.4m dish with new RA3AQ feed. G4DDK style LNA and 250W in feed. Sun noise 12.5 dB at SF=68. System noise temperature better then 40K. So with good optimized system it is possible to have a lot of QSOs on 23cm and up even with 2.4m dish.


Od: Tommy Henderson <wd5ago@hotmail.com>
Komu: moon-net@list-serv.davidv.net
Předmět: Re: [Moon-net] 2.40m dish
Datum: 26.9. 2008, 16:17 - před 4 dny

Hello Phil and EME Group I am re-posting some info I sent to Phil + other performance data. My dish is a commercial Andrews 2.4m Grid type (0.375 f/D) dish. It was given to me several years ago and was going to be use for sun noise demo's and 1420 MHz RA work for college students as I already had a HB 5.5m dish on 23cm. Moving locations in 2002 forced to sell large dish and stay ideal on EME. Then thought: what could be done on EME with 2.4m grid? With 0.25" hardware cloth placed for the reflecting surface we placed it on 6cm with 20 watts and worked W5LUA, heard F2TU and OE9ERC. That was a neat experiment then took dish down due to CCR's. Two years later I put 2.4m dish back up (4ft high) to see if anyone will say anything for RA work on 1420 MHz. Then a blessing came out of no were to the availability of 180 watt 13cm amplifiers. With that kind of power could the dish perform well on 13cm? The 13cm HB CP feed and HB LNA produced several contacts at the start and detectable echo's on 13cm. Calculated eff. was 56%. Then we experimented with higher efficiency scalar for deeper dishes. After dozens of multi-ring feeds designs built and CAd testing by W1GHZ, a 3ring was built that offered 64% eff. We also expanded the dish in 0.01 f/D steps to verify performance of feeds for deeper dishes down to 0.33 f/D for our paper. I left the dish at the expanded 2.7m and feed performance is ~60%. With other improvements like another HB LNA design change which is now running in the 0.3 dB n/f range we measure:13cm: 11.0 dB sun noise w/SFU at 66, 0.3 dB moon noise, 7.3 dB CS/G, ~28deg Dish Ta and echoes ~6dB above noise. 22 stations worked in 08' EME contest and 44 initial contacts on 13cm over 3 years. And there is no local RX problems of Wi-Fi on 2304, a little higher noise on 2320 and lots of pulse noise on 2424 but, is reduced with good noise blanker and HB higher IP Rx converter with interdigital filter for 2424 to work JA's. With the use of available, cheap, solid state power on 13cm, in my opinion, out weighs many of the other problems found on 13cm EME. We have also used the dish since the higher performance CP feed developed on 23cm, 9cm and again on 6cm. 23cm - two years ago, 2m-23cm EME contest..was board...built 3ring for dish (yes it was big in the dish!) worked 9 stations with solid state 120W in contest! 1 on SSB, Heard 28 stations, ~ 9.5 dB sn I think 9cm - sun noise about 1 dB less than on 13cm, worked 2 stations and heard 7 (only 40 watts), dish mesh a little big 6cm - sun noise also about 1 dB less than 13cm, worked 7 stations and SSB (only 20w at feed!) On 6cm I only illuminate 2.4m of dish due to outer ring not suitable for >4GHz Contacts on all bands is CW only here

I hope this information will encourage you and everyone else to populate the moon with EME signals from small dishes (for starters). Hope to see some of you at the Microwave UpDate 08, will present on above topic

Tommy WD5AGO

Od: Mark GM4ISM <gm4ism@blueyonder.co.uk>
Komu: Moon-Net <moon-net@list-serv.davidv.net>
Předmět: Re: [Moon-net] 2.40m dish
Datum: 26.9. 2008, 18:37

Hi Phil, es All,
For what its worth, my observations on the use of 2.4m dishes. On 23cm, this is enough to work many stations IF the dish is well illuminated (not too difficult these days) with 120W or so. My best QSO was with a station using a 3m dish the other end (it was very hard going, my RX performance was not the best , but was offset by the high power TX the other end.. ) This I would consider the limit of my system on CW at this power level. It puts most stations active on 23cm in reach and if JT modes were used I think I could work other 2.4m stations. There are many stations with 4m and up dishes that are really rather easy to work, and a few QSOs on random CW have been made.

Not tried 2.3GHz yet, but the same dish on 3.4GHz is pretty good, I have about 45W and a sub optimal feed (septum without choke) and have had some nice QSOs. With more work on the dish, PA and preamp I will probably be able to work other 2.4m dish stations in the 100W class Even on my modest system I have detected my own echoes on a waterfall trace..

On 5.7 GHz I operated with a 1.8m dish, (also not fully optimised) and was just marginally unable to make QSOs with several stations.. my 2.4m dish will be fine. more work required!

on 10GHz again I operated with a 1.8m dish, and worked 3m dish stations and above.. a 2.4m dish is big enough.. one day I will get the feed fitted and get back on. All my EME QSOs so far have been on CW My conclusion.. A 2.4m is well worth putting on EME on all the microwave bands. It will require a bit more effort to optimise, both on the dish and the PA and preamp front, but you will work a good number of stations and have a great time! on the plus side its easier to point than a bigger dish! Having successfully got a 2.4m dish running, you will have a really good station if you are later able to upgrade to a larger antenna. my system can be seen at www.dc2light.co.uk


Od: Greg Drzyzga <na4n@hughes.net>
Komu: moon-net <moon-net@list-serv.davidv.net>
Předmět: Re: [Moon-net] [moon-net] 2.40m dish
Datum: 26.9. 2008, 20:41

Phil FR5DN,

I started with a 10 foot dish, made quite a few contacts with the larger stations, but after awhile you frankly want to make new contacts. You find yourself hearing other stations but not being able to copy them 100 percent. To upgrade from one dish size to another can be costly. If you don't do anything else, at least put up a section of tower about 8 feet high, put a 4" mast in some sort of bearing surface, and install 2 gears around the mast one to rotate the mast and the other for the digital encoder or positioner. That way you can pretty much up grade without starting from square one. I'm using a 12 foot and now I find myself looking for something larger, at least all I need now is a larger dish.
Greg, NA4N

Od: Chris SP7DCS <sp7dcs@o2.pl>
Komu: fr5dn@izi.re
Kopie: moon-net@list-serv.davidv.net
Předmět: Re: [Moon-net] 2.40m dish
Datum: 26.9. 2008, 21:18

Hello Phil and all,

I have 3m dish and I can share my experience with you. My dish has 0.34 f/D and I use RA3AQ feed and 150W SSPA. With that setup I was able to make 29 qsos on CW random during last ARRL contest. I would work more but I was sharing time with my 2m and 70cm activity. I was able to hear much more stations with this antenna, but my small power was not enough to catch them. I agree with DL4MEA that illuminating dishes with low f/D is difficult and I think it makes my signal weaker. You can hear signals received with my station on my website - http://sp7dcs.webpark.pl (click EME signals and choose 23cm band). You can also hear how my signal was received by G4CCH with 5.4m dish on Howard's website - http://www.g4cch.com/sounds/hearsome.html It will give you some impression.

I am sure that 2.4m dish will give you also possibility to make many qsos, but you will need to have good feed, preamp and more power - Sven SM5LE is a great example of perfectly optimized station.. Of course this setup will give you a lot of fun and you will get 23cm eme bug;)

VY 73 ! de Chris SP7DCS.

Od: Luis Cupido <cupido@mail.ua.pt>
Komu: moon-net@list-serv.davidv.net
Předmět: Re: [Moon-net] 2.40m dish
Datum: 27.9. 2008, 04:49

Being one of the deep dish users (0.3) I couldn't resist to comment.

Deep dishes gained some bad reputation about feeding that is not truly fair. Long time ago, when only a few feed designs existed things were not too bright, I agree, but nowadays designs exist that can provide reasonable efficiencies (ok, slight less than eff of more shallow dishes). However deep dishes can be extremely quiet in terms of noise pickup. So taking in consideration that what really matters for EME reception is G/T and not simply efficiency or gain, things are not so negative, on the contrary you may end up with a good reception as good as the others (with the same size) or even better but may stay a 1dB or 2dB below on your TX...

... so put more volts in you PA hi ;-)

Luis Cupido

Od: Edward Cole <kl7uw@acsalaska.net>
Komu: Moon-Net <moon-net@list-serv.davidv.net>
Předmět: Re: [Moon-net] 2.40m dish
Datum: 27.9. 2008, 08:50

For what its worth, I wonder if any out there have looked at the eme pathlink as frequency increases? Pathloss rises by the square of the frequency and so does dish gain by square of diameter. So a ten foot (3m) dish should work as well at 10-GHz as it does at 1296. From what I have gleaned from reading, ten foot is the minimum "standard" for CW.

Opting for an 8-foot dish (2.4m) reduces gain by 20Log (8/10) or ~ 1.9 dB down from a 10-foot dish. That being said one would expect the same performance if sky noise, preamp NF were the same. But it seems that the smaller dish does just a bit better with higher frequencies. Could this be due to slightly lower sky temperature? Or is it because the Moon is better illuminated by the smaller beamwidth?

Ironically, today my wife tells me that there is a 14-foot mesh TVRO dish a avilable in our neighborhood for the taking. Since I have two 1.8m, a 2.4m, and a 4.9m dish, I certainly need another one ;-) I will probably retrieve the 14-foot dish if only to hold for some future eme'r or amateur radio astronomer.

Re the 4.9m dish: We are fabricating and welding the az-el mount tomorrow. This mean we should have the dish installed in about two weeks. Give me two more weeks for installing feed, running cables and 60w PA at the dish.

73, Ed - KL7UW

Od: F5HRY <f5hry@free.fr>
Komu: moon-net@list-serv.davidv.net
Kopie: moon@moonbounce.info
Předmět: Re: [Moon-net] 2.40m dish
Datum: 27.9. 2008, 09:26

Hello Phil,
Nice to hear from you. I am running a 2.40m mesh dish here with approximatly 450 W at the feed. I have some (tiny but real) echoes, and worked 66 nitials so far (and I am not very active). Thus, I think that it is not so marginal ...

Vy 73
Herve F5HRY

Od: Koellner, Guenter (NSN - DE/Munich) <guenter.koellner@nsn.com>
Komu: ext Edward Cole <kl7uw@acsalaska.net> , moon@moonbounce.info , moon-net@list-serv.davidv.net
Předmět: Re: [Moon] [Moon-net] 2.40m dish
Datum: 27.9. 2008, 10:37

Ironically, today my wife tells me that there is a 14-foot mesh TVRO dish available in our neighborhood for the taking. Since I have two 1.8m, a 2.4m, and a 4.9m dish, I certainly need another one ;-) I will probably retrieve the 14-foot dish if only to hold for some future eme'r or amateur radio astronomer.

Hello Ed,

my wife just would tell me that I should watch out if the scrap dealer comes and catches it, to give away some of my stuff. :-)
Luckily, I am joking.

73, Günter (dl4mea)

Od: FR5DN-Phil <fr5dn@izi.re>
Komu: moon-net@list-serv.davidv.net , moon@moonbounce.info
Předmět: Re: [Moon-net] 2.40m dish
Datum: 28.9. 2008, 08:03

Hello All,

Many tks for all inputs on the subject. I have no data on the F/D of that TVRO dish, so don't know if it can be expanded or not. 23cms would be too marginal, as i would need high power for decent work. Having no tools to work on these higher bands, i need no bad surprise, and no waste of time and money. I'll see what can be done with that dish...

Vy73 - Phil - FR5DN

Od: yo2is@wa7v.ampr.org
Komu: moon-net@list-serv.davidv.net
Předmět: [Moon-net] 23cm EME 'little pistol' ( Re: 2.4m dish)
Datum: 28.9. 2008, 19:26
From: YO2IS

Hello from KN05ps,
Was pleased to read so many interesting advices regarding the use of small deep dishes for 23cm EME. Being one of the happy users of a minimal setup for 23cm EME, still not yet completly optimised, am still far away from the satisfactions of my first 70cm EME activity, very well publicised in the 90's. It seems I have already lost the top of interest for 23cm EME, its a matter of fashion. Mostly the same hams do migrate slowly to higher frequencies. EME-ers are getting older and are not anymore happy to dig out from the noise the QRP signals...and then eventualy to answer the received QSL's. ( QSL always a TROPHY to show for the QRP-ers everywhere !) Just wonder if anyone is going to beat DL9KR's DXCC 70cm CW and put up a goal for an analog DXCC on 23cm ?, once again CONGRATS Jan !. Always technocrats put in front the setup, the bigger the better, rarely have read about the skils needed for top EME op's, they will always know how to handle signals of the 'little pistols'. Bravos to SM5LE !.
Cu agn on 160m DX next season.

73 & DX, Szigy, YO2IS

Od: Oene <pa3cwn@tele2.nl>
Komu: Moon <moon@moonbounce.info> , Moonnet <moon-net@list-serv.davidv.net>
Předmět: [Moon] 2.40 m dish
Datum: 29.9. 2008, 11:34

Thanks everyone for their answers on this topic started by Phil FR5DN I will dive into this matter t and hope to be qrv in the future on the 23 cm band. In general it is clear to me that a 2.40 dish is minimal and maybe 5m is more likely to have good succes and lot's of you referring to the pages of SM5LE which I will study thouroughly.

Best 73 and GL to all