Keyboard Shortcuts
ctrl + shift + ? :
Show all keyboard shortcuts
ctrl + g :
Navigate to a group
ctrl + shift + f :
Find
ctrl + / :
Quick actions
esc to dismiss
Likes
Search
Locked Re: Is this Wellbrook wide aperture loop faulty?
|
Hello Tom,
toggle quoted message
Show quoted text
Monday, January 3, 2022 This TS-590S that I have had for donkey's years has been great on LF, both RX and TX, but the start of its ills came when I managed to transmit a kilowatt of RF INTO th RX port. I fixed it but it has since had other issues and now has a fade on RX problem that seems heat related. It's time to put it out to pasture and either buy a new one or something similar. I use a Red Pitaya and pre amp and the Kiwi plus some Softrocks for RX as well as the 590, but only the Red Piataya could be made to TX as well. Best regards, Chris mailto:chris@... TCG> Sounds like you are making great progress Chris. TCG> I doubt that a new TCVR will make much of a difference. Most of TCG> them will have filtering to reduce sensitivity at LF/MF. This is TCG> to reduce the likelihood of problems at HF, like spurious breakthrough etc. TCG> Is there any chance you could borrow a modern rig and prove me wrong? TCG> Tom G6PZZ TCG> -----Original Message-----
TCG> From: [email protected] <[email protected]> On Behalf Of Chris Wilson TCG> Sent: 03 January 2022 09:34 TCG> To: Alan <[email protected]> TCG> Subject: Re: [loopantennas] Is this Wellbrook wide aperture loop faulty? TCG> Hello Alan, Martin et al, TCG> Saturday, January 1, 2022 TCG> People must be getting bored with my saga by now, so I will TCG> keep it as short as I can. Basically, yesterday lent me the TCG> opportunity to do some more tests. Running the injector box off a TCG> 12V accumulator made zero noticeable difference. Running the KIwi TCG> as well, off my mobile phone 5V power pack made a minute TCG> difference to overall noise. Disconnecting the coax to the TCG> antenna at the injector box still left some strong signals. TCG> Wrapping about 10 turns of the coax out to the loop around a BIG TCG> ferrite ring (I have the spec but can't recall it off hand) made a noticeable difference. TCG> Then I had the idea to wrap the short (2 foot or so) of coax TCG> from the injector box to the Kiwi as many turns as possible TCG> around a similar ferrite ring. I think I got about 5 or six turns TCG> on, the BNC plug limited this. Now THAT made a big difference! TCG> I am pretty pleased to have persevered and enormously grateful to those who stuck with me. TCG> Downside is MF / LF amateur digital performance has markedly TCG> deteriorated. Is it the smaller circumference of the new loop? TCG> The 30 to 35 or so degrees rotation of the loop form its TCG> orientation looking down from the sky (plan view)? Originally the TCG> loop in plan view ran almost east to west, it's now skewed about TCG> 35 degrees or so anti clockwise and a bit lower overall.... TCG> Testing has been made a bit problematic as my TS-580S which has TCG> had a hard, no, very hard life, has started to lose sensitivity TCG> and sometimes goes totally dead on receive. It seems heat TCG> related, but it's years old and had one incident where I managed TCG> to shove a kilowatt of LF 137 kHz up the receive antenna port. TCG> Needless to say it didn't like it and I amazed and astounded TCG> myself by managing to repair it with my scope and a sig gen. More TCG> good luck, strong coffee and a good light source, plus a huge TCG> taped together print out of the schematic. TCG> I think I might treat myself to a newer (if still secondhand) TCG> rig soon. As an aside what modern transceivers hear well at LF TCG> and MF and will TX a milliwatt or so on LF and MF to act as an TCG> exciter, anyone here any experience of anything suitable or TCG> should I just get a newer TS-590? TCG> Critical comments welcome: TCG> TCG> Thanks again everyone. TCG> Best regards, TCG> Chris mailto:chris@... A>> Martin A>> As Andrew said shorting the input is not a good idea and will not do A>> what you think it will. Leaving the terminals open will but you need A>> to disconnect both terminals. The amplifier is a Zwischenbasis type, A>> as you have plotted in the past the input reacts to the signal source A>> impedance. This form of noiseless feedback is the complement to the A>> Norton Amplifier where the output impedance is a transformed version A>> of the input impedance, here the output impedance hardly matters but A>> you get to optimise the matching to the source over a much wider A>> range than a conventional "dumb" input , it is NOT a virtual earth A>> amplifier in the normal sense ( which also goes nuts with a shorted A>> input !) but a much cleverer configuration due to Cantz from 1953. A>> However before disconnecting the loop I would remove the power to A>> the injector then disconnect the coax to the injector. That would A>> show what is leaking into to the coax and then what remains after the A>> coax is removed. It seems futile to disconnect the loop when you can A>> just power it down. A>> I used a naked ALA100LN until recently, it works very well from LF to A>> HF and beyond. The IMD performance is outstanding six miles from A>> Brookman's Park. I now use a new arrangement that drops BP signals A>> an additional 30dB. I spot to PSK reporter from a tiny urban back A>> garden, Don't do too bad for an antenna 3m high surrounded by A>> switchers although BT has blocked 30m very effectively. A>> 73, Alan G8LCO. TCG> |
to navigate to use esc to dismiss