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Locked Active loop antenna
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jr_dakota
You need strict 50 ohm input and output impedances for these MMICs to
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work properly which is kind of hard to do with the first amplifier on a broadband antenna ... On a tuned loop with a small pickup loop it would probably be alright but a plain ol' RF transistor would work as well or better You also have to be real careful applying a 1 Ghz amplifier for use in the HF range because they have a tendency to 'go off' (Oscillate) in the VHF range where you can't hear (And most people can;t see on their scope) the result in the receiver but other than it's not working right (Little or no gain, front end blocking, etc) Personally I don't like to use them other than in transmitting amps for the HF range, when you start getting into 2 Meters and up though they are hard to beat because you can get decent gain and IP3 without tuned circuits where the difference between a 2 1/2 turn inductor and a 3 turn inductor can be several Mhz JR --- In loopantennas@..., "exnci2000" <awfhgm@...> wrote:
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Keith Browning
How about a plain old FET to lower the loading?
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Keith ----- Original Message -----
From: "jr_dakota" <SG2112@...> To: <loopantennas@...> Sent: Friday, March 02, 2007 10:09 AM Subject: [loopantennas] Re: Active loop antenna You need strict 50 ohm input and output impedances for these MMICs to work properly which is kind of hard to do with the first amplifier on a broadband antenna ... On a tuned loop with a small pickup loop it would probably be alright but a plain ol' RF transistor would work as well or better You also have to be real careful applying a 1 Ghz amplifier for use in the HF range because they have a tendency to 'go off' (Oscillate) in the VHF range where you can't hear (And most people can;t see on their scope) the result in the receiver but other than it's not working right (Little or no gain, front end blocking, etc) Personally I don't like to use them other than in transmitting amps for the HF range, when you start getting into 2 Meters and up though they are hard to beat because you can get decent gain and IP3 without tuned circuits where the difference between a 2 1/2 turn inductor and a 3 turn inductor can be several Mhz JR --- In loopantennas@..., "exnci2000" <awfhgm@...> wrote:
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Fraser
Hi Franco,
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The AOR WL500 uses a MAR6 MMIC from Minicircuits as it's RF amplifier. The WL500 is varacap diode tuned and uses "bulk inductance" in the form of two switched fixed inductors to bring the 2 turn loop to resonance at the required frequency. I was VERY surprised to see the MAR6 attched directlt to the output of the tuned loop as it is a 50 ohm inout and output device. I would never have used such a device in a tuned loop design myself. AOR made it work though and the WL500 was apparently a pretty decent tuned HF Loop. It is now discontinued. I do have the schematic of the AOR WL500 if you need it but the two fixed loop inductors are not detailed either in type or inductance value so some experimentation may be required. You could do worse tan buy a Degen DE31MS as they are so cheap from China via eB*y. You could then experiment with that design to improve it if required. PM me you email address if you want the schematic. Regards Fraser --- In loopantennas@..., "exnci2000" <awfhgm@...> wrote:
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Rob Moore
Hi,
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I'd like a copy of the WL500 schematic! It will save me a lot of trouble tracing through the wiring and PC board. Regards, Rob --- In loopantennas@..., "Fraser" <fraser.castle@...> wrote:
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Fraser
Rob,
Email me and I'll add you to the list of email recipients for the schematic. Fraser --- In loopantennas@..., "Rob Moore" <rmoore5@...> wrote: wrote: amplifier. the form resonanceof two switched fixed inductors to bring the 2 turn loop to output ofat the required frequency. neverthe tuned loop as it is a 50 ohm inout and output device. I would it workhave used such a device in a tuned loop design myself. AOR made Loop. Itthough and the WL500 was apparently a pretty decent tuned HF twois now discontinued. inductancefixed loop inductors are not detailed either in type or fromvalue so some experimentation may be required. improveChina via eB*y. You could then experiment with that design to mololithic Rfit if required. if youamplifier ERA/MAR series offering good IP3.I would like to know loophave some schematich diagram to homebrew an active broadband antenna from 100 Khz to 30 Mhz !! |
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Ralph Lane
Hi, add me to the list for the Loop antenna schematic.
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Ralph ----- Original Message -----
From: "Fraser" <fraser.castle@...> To: <loopantennas@...> Sent: Friday, March 02, 2007 11:55 AM Subject: [loopantennas] Re: Active loop antenna Rob, |
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Fraser
Hi Ralph,
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You will need to PM me your email address. Fraser --- In loopantennas@..., "Ralph Lane" <rlane7301@...> wrote:
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Ralph Lane
My email address is Rlane7301@...
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Ralph ----- Original Message -----
From: "Fraser" <fraser.castle@...> To: <loopantennas@...> Sent: Friday, March 02, 2007 6:14 PM Subject: [loopantennas] Re: Active loop antenna Hi Ralph, |
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jr_dakota
A FET might be alright, definitely the ticket on short whip with a
high impedance .... I'm not sure what the impedances look like on a (relatively) short untuned loop, I tried to measure one with my AMQRP Antenna Analyst but I have way too much metal (heat ducts, pipes, etc) in my basement to get an accurate reading so I need to wait a few more weeks for the weather to warm up so I can take it outside in the free and clear and get some measurements I will say this though, expect a Wellbrook clone from me by the end of April using a push-pull pair of 2N5109s (or similar) and perhaps a pair of FETS depending on the impedances or the need for more gain JR --- In loopantennas@..., "Keith Browning" <kbrowning@...> wrote: the Links rather than uploading the file.and GIF into Photos. Please convert BMP or TIF to JPG or GIF before uploading. |
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In a message dated 09/03/2007 00:30:06 GMT Standard Time,
preynaert@... writes: Probably a careful electrician could easily open it up and find out, what is ticking in it.... Of course any transistor can be identified without any text available on it, but who could diagnose a microprocessor the same way? That has already been done! But I'm not so sure if it is legal to make it public. -------------------------------------- Oh good..... can you at least tell us what microprocessor it uses? |
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aimo ruoho
Fine!
A WELLBROOK CLONE! Please tell us more about it. I have been trying hard to buy one, but nobody ever answered my many emails from England............... So I have tried to build one of my own. I have many "prototypes" in my listening room and in the attic, but I am not yet satisfied with them. It's the electronics inside the small box, which is the most important part of the famous Wellbrook, if I understood right. Probably a careful electrician could easily open it up and find out, what is ticking in it.... Of course any transistor can be identified without any text available on it, but who could diagnose a microprocessor the same way? Perhaps the Chinese will soon make a cheap and, hopefully better and freely available, clone? So let's be in touch with each other and eBay! Aimo, the simple homebrewer of electronics. jr_dakota <SG2112@...> wrote: A FET might be alright, definitely the ticket on short whip with a high impedance .... I'm not sure what the impedances look like on a (relatively) short untuned loop, I tried to measure one with my AMQRP Antenna Analyst but I have way too much metal (heat ducts, pipes, etc) in my basement to get an accurate reading so I need to wait a few more weeks for the weather to warm up so I can take it outside in the free and clear and get some measurements I will say this though, expect a Wellbrook clone from me by the end of April using a push-pull pair of 2N5109s (or similar) and perhaps a pair of FETS depending on the impedances or the need for more gain JR --- In loopantennas@..., "Keith Browning" <kbrowning@...> wrote: the Links rather than uploading the file.and GIF into Photos. Please convert BMP or TIF to JPG or GIF before uploading. --------------------------------- Finding fabulous fares is fun. Let Yahoo! FareChase search your favorite travel sites to find flight and hotel bargains. |
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Patrick Reynaert
Hi,
Probably a careful electrician could easily open it up and find out, what is ticking in it.... Of course any transistor can be identified without any text available on it, but who could diagnose a microprocessor the same way? That has already been done! But I'm not so sure if it is legal to make it public. Patrick. --------------------------------- The fish are biting. Get more visitors on your site using Yahoo! Search Marketing. |
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Patrick Reynaert
It was a ZTX337 (the marking on the transistor was not even erased). I never got an hold of a ZTX337, but the circuit works also with matched 2N5109 transistors with comparable OIP3 and OIP2 figures.
It was an old unit that I broke open. I'm not sure what Andy made different in the newer versions of the ALA. Pat. gandalfg8@... wrote: Oh good..... can you at least tell us what microprocessor it uses? --------------------------------- 8:00? 8:25? 8:40? Find a flick in no time with theYahoo! Search movie showtime shortcut. |
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Greg W:-)
--- In loopantennas@..., gandalfg8@... wrote:
-------------------------------------- If there is a processor Its probably a PIC. But ,, who in their rite mind would put a processor in a box containing a high gain amplifier. I doubt they would go all the way needed to make the chip quiet. The whole idea of loops is to reduce noise , and adding an osciolator and processor in there doesn't help the cause. gregW:-) ======================================================================= |
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In a message dated 10/03/2007 08:45:02 GMT Standard Time,
c.beijersbergen@... writes: And BTW, what should the microprocessor be doing in there? -------------------------------------- It's used for the automatic tuning. In order to cover the wide bandwidth the antenna has to be electronically tuned to the correct operating frequency and this is done by rapidly sweeping the tuning across the whole band and monitoring for the point at which energy absorbed by the radio is greatest as this will correspond to the tuned frequency of the radio. Fortunately, even a modest microprocessor can scan much faster than a human operator, or even the fastest scanner, so this process can be repeated rapidly and remain transparent to the operator. When a predermined number of scans return the same result the tuning remains fixed but the energy absorbed continues to be monitored. If the absorbed energy returns to the pretuned value, or decreases to a significant extent, it is assumed the radio tuning has changed and the whole process repeats. This all happens millions of time a second, so is never obvious to the user, and part of the design process has to establish the proper times for tuning period and dwell in order to ensure that no tuning lag occured whilst minimising the need for repeat cycles. This great advance in antenna technology is the subject of a number of patent applications and the electronics are potted in order to protect the designer's intellectual property rights. |
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Greg, if a processor is needed, the tuning cycle would be the only
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time that the processor is require to operate after which, the processor can by cycled back to a very low clock rate, or put into sleep mode for quite reception. Best regards, Paul WA5LFY --- In loopantennas@..., "Greg W:-)" <onegammyleg@...> wrote:
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Greg W:-)
¡§what should the microprocessor be doing in there?¡§
Exactly !. I just looked at the welbrook site and I didn't see any mention of a microprocessor in their latest antenna. Perhaps I'me wrong , but I don't think there is a processor in there at all. Perhaps a previous message writer saw (or heard of) a chip inside and confused that with a processor , where as in reality , it might have been a voltage regulator or a mosfet in an odd package.(who knows?) As far as your question is concerned , I just cant image a use for a microprocessor in an active RX antenna like that. gregW:-) =================================================================== --- In loopantennas@..., "C. Beijersbergen" <c.beijersbergen@...> wrote:
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Greg W:-)
I don't believe it.
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gW:-) ======================================================================= --- In loopantennas@..., gandalfg8@... wrote:
SNIP electronically tuned to the correct operating frequency and this is done by rapidlysweeping the tuning across the whole band and monitoring for the point atwhich energy absorbed by the radio is greatest as this will correspond to the tunedSNIP |
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