This is a very early model and just looking at it there are some issues, 1 the capacitor is in the wrong position, 2 the capacitor looks like it has no resistance when you turn it, this is probably due to the nut and spring washers need to be tightened, you should get an swr on 1.3 or less on 40 metres, like an old car thats been through some owners if its not been looked after then it could do with a good service, I can give it a total overall and get it working for you for £40.00 +P&P thats a total overhall and a new style capacitor fitted. Adrian (2E0ERO)
You should disconnect the capacitor from the main loop before trying to test it for shorts. Also disconnect the matching loop from the coax before testing both of them. A vna would help you to identify where it is resonant once you have established the connections are ok. Resonance might not be the same as low VSWR. The problem could be a basic connection issue or could be that the matching loop needs adjusting. Usually you would see a butterfly capacitor or a vacuum capacitor used on transmitting loops. Sharp edges on a high voltage capacitor are also not good.
Hello Jez its a much finer tune than that :) as its very high Q so you could try connecting to a radio and tune for the most noise but it very fine movements
The bottom fin on the capacitor looks like it gets rather close to the other fin's. Also check the connections to the capacitor, especially the center connector where it rotates, could possibly need to be tightened up. Is that another capacitor in series underneath in a black wrapper? Possible that its had too much power and its blown that up. Its only QRP. Problem is definitely the capacitor. Don't forget that its Adrian that works at Moonraker who makes these. Not as Moonraker however as his sideline.
From what you've shown so far jezz there's no reason why that loop shouldn't work, the inner loop is an inductive coupler and should show a short circuit when you do a continuity test, looking at the tuning capacitor the vanes look ok check where both wires connect to the capacitor it should read as open circuit if it shows a short there you may have a problem, in the video one of the wires leading up to the capacitor looked loose make sure all the terminals are tight, could also make sure that the inductive coupler is closer to the main loop as well.
1. Disconnect the capacitor and verify it is OPEN (no beep on meter). I see that the bottom part of the capacitor is not evenly spaced when rotated. It will arc. Gently bend the plate so that it is centered during full rotation of travel. If you have access to an LCR meter, you can verify and measure the capacitor. 2. This is a double turn coil and it will therefore have less efficiency vs a single turn coil, so don't expect it to perform well. 3. By the looks of the homemade design, I would not put more than 10 watts into the loop. 4. Check the resonance with the capacitor disconnected. It should be somewhere around the 10M band. The capacitor is in parallel with the loop and lowers the resonant frequency, but it also lowers the radiation efficiency. Highest output of RF will always be on the highest frequency where less capacitance is needed. 5. Consider using a good choke on the feedline where it connects to the primary (smaller coil) of the antenna to remove common mode RF on the feedline. Good luck and 73
you can not tune a loop with a vna as it will see it as a short yes it should have a short now connect it to a radio and the move the capacitor to tune for max noise then its just very fine movements to lower the VSWR
This is a very early model and just looking at it there are some issues, 1 the capacitor is in the wrong position, 2 the capacitor looks like it has no resistance when you turn it, this is probably due to the nut and spring washers need to be tightened, you should get an swr on 1.3 or less on 40 metres, like an old car thats been through some owners if its not been looked after then it could do with a good service, I can give it a total overall and get it working for you for £40.00 +P&P thats a total overhall and a new style capacitor fitted.
Adrian (2E0ERO)
Cant be fairer than that 🙂would still be a bargain, I have been interested in one of these loops for a while.
Seems fair..
Can't wait to receive mine Adrian. Ordered a few days ago on ebay :)
@MI7DJT how did you get on with the loop?
You should disconnect the capacitor from the main loop before trying to test it for shorts. Also disconnect the matching loop from the coax before testing both of them. A vna would help you to identify where it is resonant once you have established the connections are ok. Resonance might not be the same as low VSWR. The problem could be a basic connection issue or could be that the matching loop needs adjusting. Usually you would see a butterfly capacitor or a vacuum capacitor used on transmitting loops. Sharp edges on a high voltage capacitor are also not good.
Hello Jez its a much finer tune than that :) as its very high Q so you could try connecting to a radio and tune for the most noise but it very fine movements
Your sort it out Jez, you always do. 👍😉
The bottom fin on the capacitor looks like it gets rather close to the other fin's.
Also check the connections to the capacitor, especially the center connector where it rotates, could possibly need to be tightened up.
Is that another capacitor in series underneath in a black wrapper? Possible that its had too much power and its blown that up.
Its only QRP. Problem is definitely the capacitor.
Don't forget that its Adrian that works at Moonraker who makes these. Not as Moonraker however as his sideline.
THANKS JEZ
From what you've shown so far jezz there's no reason why that loop shouldn't work, the inner loop is an inductive coupler and should show a short circuit when you do a continuity test, looking at the tuning capacitor the vanes look ok check where both wires connect to the capacitor it should read as open circuit if it shows a short there you may have a problem, in the video one of the wires leading up to the capacitor looked loose make sure all the terminals are tight, could also make sure that the inductive coupler is closer to the main loop as well.
Ill give it a try cheers
If you contact, Adrian 2E0ERO he will service the aerial for you because I spoke to him about your issue.
Thankyou
@@2j4ezhe replied above
Ordered one of these myself a few days ago Chris. Looking forward to playing with it!
god job
1. Disconnect the capacitor and verify it is OPEN (no beep on meter). I see that the bottom part of the capacitor is not evenly spaced when rotated. It will arc. Gently bend the plate so that it is centered during full rotation of travel. If you have access to an LCR meter, you can verify and measure the capacitor. 2. This is a double turn coil and it will therefore have less efficiency vs a single turn coil, so don't expect it to perform well. 3. By the looks of the homemade design, I would not put more than 10 watts into the loop. 4. Check the resonance with the capacitor disconnected. It should be somewhere around the 10M band. The capacitor is in parallel with the loop and lowers the resonant frequency, but it also lowers the radiation efficiency. Highest output of RF will always be on the highest frequency where less capacitance is needed. 5. Consider using a good choke on the feedline where it connects to the primary (smaller coil) of the antenna to remove common mode RF on the feedline.
Good luck and 73
I’ll give it a try thanks for the information
you can not tune a loop with a vna as it will see it as a short
yes it should have a short now connect it to a radio and the move the capacitor to tune for max noise then its just very fine movements to lower the VSWR
Yes I need to connect it to a radio will use my ft817 and give it a try
black on bottom is really loose