any working EME

[VK1JA]

G'day Alan,

The setup that I have at the moment isn't the setup that I'd be trying eme with, but only the antenna's and last run of cable will change. Currently for 2m and 70cm I have a pair of 'cheap yagi's' in vertical pol for sat work. The 2m yagi is 4el and the 70cm is 8el - I hope that the noise floor will reduce when I get the 7el lfa yagi up for 2m. The 70cm will change to a homebrew 15el yagi.

My full setup is:
TS-2000 for the radio - Cables for 2m and 70cm are separate cables, but identical - 30cm RG213 patch cable to a bias tee (to feed power up the coax) then a 10m run of LDF450 to switching relays (switch between a vertical antenna for repeaters and the yagi's for sat work), then 4m run of RG213 to the 2m and 70cm cheap yagis. When I get the 2m lfa and homebrew 70cm yagis in the air then the 4m run of RG213 will be changed to SCF12-50J cellflex to reduce cable loss.

Pre amps are boom mounted ARR units, MSP144VDG-160 for 2m (0.55dB NF and 24dB gain) and MSP432VDG-160 for 70cm (0.55 dB NF and 16dB gain).

With the TS-2000 pre amp on and the ARR pre amp on the noise floor is (just checked) S4 pointing west (S2 when pointing up 45 degrees), but when I swing the yagi around to the SE it climbs to S10+ (S7 pointing up at 45 degrees) !! I have a feeling the 'cheap yagi' is half to blame and (fingers crossed) the noise floor will reduce when I get the lfa up. Without the ARR pre amp on the noise floor drops to ZERO on 2m !! 70cm is all fine with the noise floor at zero or maybe S1-2 at the highest.

I haven't had a good play with the DSP on teh TS-2000 yet, do you narrow the filters right down? What cut off's do you usually run at for the filters?

Loooong term I might look at 2 x lfa's for 2m and 2x lfa's for 70cm. but that's loooong term.

Cheers

Is that S6 in all directions? What antenna design are you currently using?

On moonrise I have up to S9 at the horizon, but that drops off rapidly above 30deg above the horizon. I think that's part of the reason there are so many Europeans on the moon, but none of the regulars are running dated yagi designs.

How much gain do you have from your preamp? Have you tried a different one? Could be simple front end overload. What's your noise floor without the preamp? Do you have DSP? Without the DSP in the IC-7000 I probably wouldn't hear much here either.

[ZL4PLM]

G'day Alan,

My full setup is:
TS-2000 for the radio - Cables for 2m and 70cm are separate cables, but identical - 30cm RG213 patch cable to a bias tee (to feed power up the coax) then a 10m run of LDF450 to switching relays (switch between a vertical antenna for repeaters and the yagi's for sat work), then 4m run of RG213 to the 2m and 70cm cheap yagis. When I get the 2m lfa and homebrew 70cm yagis in the air then the 4m run of RG213 will be changed to SCF12-50J cellflex to reduce cable loss.

Pre amps are boom mounted ARR units, MSP144VDG-160 for 2m (0.55dB NF and 24dB gain) and MSP432VDG-160 for 70cm (0.55 dB NF and 16dB gain).

With the TS-2000 pre amp on and the ARR pre amp on the noise floor is (just checked) S4 pointing west (S2 when pointing up 45 degrees), but when I swing the yagi around to the SE it climbs to S10+ (S7 pointing up at 45 degrees) !! I have a feeling the 'cheap yagi' is half to blame and (fingers crossed) the noise floor will reduce when I get the lfa up. Without the ARR pre amp on the noise floor drops to ZERO on 2m !! 70cm is all fine with the noise floor at zero or maybe S1-2 at the highest.

Looking at what you have written here I would say that you are simply overloading the receiver with noise

The use of a preamp should be to a) reduce the overall NF of the system by using a low noise device as close to the antenna as possible and b) overcome any cable loss

The system should be balanced knowing what the cable losses are and what the preamp gain is.

As you have said.....

" Cables for 2m and 70cm are separate cables, but identical - 30cm RG213 patch cable to a bias tee (to feed power up the coax) then a 10m run of LDF450 to switching relays (switch between a vertical antenna for repeaters and the yagi's for sat work), then 4m run of RG213 to the 2m and 70cm cheap yagis."

then you probably have very minimal cable losses - a 10m run of LDF4-50 will have perhaps 0.5 dB loss at 144 plus a couple connectors and the 4m and 0.3m run of RG214 again minimal - say 1.5 db - so you maybe have 2dB feeder loss at best.

But you have 24 db of gain at the preamp - then compounding that with the preamp on the TS2000 as well.

You have the evidence too - you said "Without the ARR pre amp on the noise floor drops to ZERO on 2m"

In my system I have a Kuhne 0.3 dB NF preamp that has 28 dB of gain and about 4 db of loss through a multitude of N types on the feeder/splitters and preamp relays - plus 35m of LDF4-50 and some patches in the shack.

I have a 20 dB attenuator on the output of the preamp - the IC9100 has its 144 rx gain set so that with the preamp on I barely hear the background noise change - so the system is balanced ... it has 0.3 db NF at the masthead and enough gain to overcome the cable loss while not overloading the receiver.

Given the low loss of the cables I would remove the ARR preamp for now - unless you can easily get into it and reduce the gain - I don't know that device - perhaps it has some gain control

But what you want is the noise level with any preamp in just raising the noise floor slightly that means it overcomes the cable loss and no more.

Anything else is bad and will actually reduce your overall MDS (maximum discernible signal) because you will mask it in noise.

Best option is to download the EME calculator from VK3UM site - you can punch numbers into that and see what the outcome is.

But I think your problem is not local noise but preamp overload as the overall system has too much gain.

Hope thats a help to getting you moving in the right direction

Cheers

Simon ZL4PLM

[VK1JA]

Thanks for the reply Simon, that certainly would make sense that I'm simply overloading the reciever. I did a bit of testing last night and found that running the ARR pre amp with the TS-2000 pre amp turned off gave me a better outcome rather than using the internal pre amp of the TS-2000 by itself.

I've downloaded VK3UM's amazing piece of software and will have a good play with it over the next few weeks.

I'm just starting to realise that working EME is an art form !

Thanks again