Hi,
This is a test setup. The VCO is missing and a standard oscillator is beeing used to test operation. The good news is that a 10 MHz output is available !!!
Has the design and code for GPSDO this been published anywhere ?
Hi,
This is a test setup. The VCO is missing and a standard oscillator is beeing used to test operation. The good news is that a 10 MHz output is available !!!
Has the design and code for GPSDO this been published anywhere ?
Has the design and code for GPSDO this been published anywhere ?
Hi, this is : Lars GPSDO , I finally use updated code (variable TC) from PA3FYM modified by me.
Hi,
A PE4302 parallel step attenuator was added to the 28/430-739 transverter. Two BCD switches was added, omitting 8 on both switches as 6 bit (3+3) is required.
Project is now consirded closed !!!
Hi,
Modification of Amiko L108 LNB for external 25 MHz.
Hi,
A dual feeder using modified Amiko L108. SWR is about 1:1.5.
Hi,
The conclusions from testing dual feeder are :
1) No important Tx signal drop exists due to LNB lens that exist inside helix.
2) Rx is desensed while Tx-ing and is not usable (in my case is not a problem as I plan to use only half duplex).
3) SNR (while not Tx...) is reduced by more that 10 dB comparing to LNB standalone operation. The obvious explanation is that helix blocks the Rx signal.
Any similar experencies from others for 2 & 3?
The only way TX should be able to desense RX is for there to be significant 10/12 GHz energy from harmonics of 2.4 GHz. The 2.4 GHz fundamental will not get through the waveguide - (as long as it is long enough, which it should be). Does the same desense occur with a patch rather than a helix?
The only way TX should be able to desense RX is for there to be significant 10/12 GHz energy from harmonics of 2.4 GHz. The 2.4 GHz fundamental will not get through the waveguide - (as long as it is long enough, which it should be). Does the same desense occur with a patch rather than a helix?
Hi,
I do not have try patch yet. I have a 10.2-15GHz bandstop filter that may solve the problem, it has about 0.5 dB loss at 2.4 GHz.
3) SNR (while not Tx...) is reduced by more that 10 dB comparing to LNB standalone operation. The obvious explanation is that helix blocks the Rx signal.
I made the same observation with my Winkler-Helix when I tilt it a little bit downwards.
If the helix is horizontal there is no loss of RX signal. Your observation is right, tilt your helix a little bit upwards if the LNB is under the helix.
This is a good idea and should work for smaller dishes too. The 2.4 GHz beam will not be correct, there will be an elevation error, but this will not matter very much because the 2.4 GHz beamwidth is relatively wide. It could be several degrees out before it matters. If we assume a 3 degree error with a 1m dish we would lose 3dB on TX. A 3 degree error on a 2.4m dish is much more serious, 10 dB down, but of course the distance to the feed is twice as far, so the angular offset for the same physical offset will be smaller and it will all equalise. Offsets have a real advantage as the focal length is usually longer meaning the feed is farther away from the dish and therefore the relative error less.
HB9SKA The LNB is inside the helix.
George, I refer to this pics from you:
Hi,
A dual feeder using modified Amiko L108. SWR is about 1:1.5.
There I can see the helix and a recess for the LNB. If the LNB is inside the helix then it is another effect.
Edit: or the same ? ...
Sorry, I can not understand! I have a Rx signal drop , more precise SNR drop about 10 dB. The Tx is OK. What is your proposal?
The proposal is to have the LNB and Helix not together but offset from one another, e.g. the helix above the LNB. This will impact TX efficiency because the beam is no longer precisely towards the satellite but hopefully not by too much as the beam at 2.4 GHz is 4 times as wide as it is at 10 GHz.
The proposal is to have the LNB and Helix not together but offset from one another, e.g. the helix above the LNB. This will impact TX efficiency because the beam is no longer precisely towards the satellite but hopefully not by too much as the beam at 2.4 GHz is 4 times as wide as it is at 10 GHz.
OK I got it. I have try this and I have seen the Tx drop.
You will see the TX drop, the question is by how much and is it an acceptable compromise?
OK I got it. I have try this and I have seen the Tx drop.
Also this effect I've observed with my Winkler-helix. Offset your helix a little bit to left seen from antenna to dish. Post an actual photo pse.
Also this effect I've observed with my Winkler-helix. Offset your helix a little bit to left seen from antenna to dish. Post an actual photo pse.