To: | <[email protected]> |
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Subject: | R: RE: Re: Antenna resistance (Re: LF: EbNaut Autodecoder 137490 Hz: EA5DOM received) |
From: | "[email protected]" <[email protected]> |
Date: | Tue, 30 Oct 2018 13:28:09 +0100 (CET) |
Reply-to: | [email protected] |
Sender: | [email protected] |
Hi Luis, LF fine also from my side I'm planning a long funny weekend between repairs, adjustment and something new ;-) Just a further question: you wrote that your analyzer gives a lot of possible outputs.. and I'm a bit confused for the display SWR (what iis it? :-D ) and module of impedance. Could you display the same datas as a Smith chart? in this way you could see both resistive and reactive parts of the complex impedance changing with frequency which is helpful to understand what is going on. Pictures you shared show SWR vs frequency and |Z| vs. frequency but shows the R±jX form only on one frequency Marco, IK1HSS
----Messaggio originale---- Da: [email protected] Data: 30-ott-2018 12.23 A: "[email protected]"<[email protected]> Ogg: RE: Re: Antenna resistance (Re: LF: EbNaut Autodecoder 137490 Hz: EA5DOM received) Hi Marco, LF The pipe runs inside the building in a narrow space. You are right, it is preserved from rain and there should be no effect
at all It has been working nice in MF so far, and also first tests in LF were very succesful. Last year I could even make a QRSS
QSO with 9A3KB using the Ropex PA with minor modifications Many variables here. I will rechek connection to the top section of the pipe, which may be failing. And then dropping
the wire parallel to the pipe if possible. We have a long weekend ahead which can be ideal for this activities …. at limit ;-) >> My new 2nd DC receiver for MF is in service since a full day so for some time I'll listen
to MF wspr, see you later on LF More rain here today and antenna wires are down. But sourprisingly I could not get RF current yesterday even with low
impedance Time to recheck PA with dummy load. May be I have a failure there too
L Oscar, LU1DOW had a fantastic night yesterday in MF. Spots from the States and again LA2XPA May be he can try to send an EbNaut message and check if we can finally receive him in central and south EU 73 de Luis EA5DOM De: [email protected] [mailto:[email protected]]
En nombre de marcocadeddu@tin.it Hi Luis, Hi Markus, LF
The pipe contains presurized water for the fire extinguish system. Is a "wet colum" system. Pipe segments are connected with big brass links. Should be a good enought current conductor. Down in the basement it connects with a pressure pump and a water reservoir tank, linked to the water grid system Will have to check the ground connections of all this stuff when possible. Not easy But after all, we are all doing all this "not easy" things because it is not easy to work low bands, right? ;-) Tested mains ground connection too and it helps a lot, but still depends on rain. Access to the ground line at the lifts engines room on top building is complicated too, as I have no access there because of a AMHPS (Anti Mad Ham Protection System) hi, hi Installing my own ground line may be an option, but using light cable. As I can only support the 80m cable at the top end, so weight must be low. Finally may be the best way to go 73 de Luis EA5DOM De:
[email protected] [[email protected]] en nombre de Markus Vester [[email protected]] > Something gets wet in the basement and the pipe gets a better connection to ground, or at least to the water grid pipes, which finally run underground
Hi All, LF
Interesting topic. Also happens in MF but in LF it gets more critical. Must be a nightmare at VLF :( As Marco explained, our setup is not the usual at ground level in a property plot. And in my case ther ground is 80m away down from the feed point, coil and capacitive topload. Measured with the antenna analyzer I can see a drop in the impedance module when all gets wet by rain It is not only an increase of RF current. Today I measured resistance from the ground side of the feed point trought the pipe to building basement and then returning via the water grid connecting the other side of the multimeter to a water pipe in my house: 4 Ohm measured early morning when it started with soft rain. At noon we had stronger rain and in the afternoon I measured again. It dropped to 2 Ohm. Big difference. Something gets wet in the basement and the pipe gets a better connection to ground, or at least to the water grid pipes, which finally run underground The top of the antenna is dismantled during storms, so can't measure impedance with the analyzer right now but bet it is now well under 30 Ohm and would drain a few amps Other intringuin detail. When it is dry and impedance rises to >100 Ohm the only way to hardly reach 1A RF is to detune the antenna. I have to set the resonant peak at 138Khz and then at 137,5 get even higher impedance and high SWR, but the antenna current rises and so the radiated signal. All this at the cost of more amps consumed by the PA and higer voltage at antenna feed. Running the antenna at the optimum resonance makes almost no RF current, even considering that this is the minimum impedance point. About the LPF, this is really the only part of the Ropex PA still in use. This is a link to the schematic with the LPF Have not tried without LPF. The analyzer measurements are made directly to antenna. But may be a good idea to make them with the LPF inserted and see what happens 73 de Luis EA5DOM De:
[email protected] [[email protected]] en nombre de
[email protected] [[email protected]] Hi Paul, Luis, Markus, LF |
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