Message-ID: <4EEE15E7.9080608@freenet.de>
Date: Sun, 18 Dec 2011 17:33:43 +0100
From: wolf_dl4yhf <dl4yhf@freenet.de>
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To: rsgb_lf_group@blacksheep.org
References: <CAA8k23Rn9WpQM3Ukf=cq5-bLmWy+o4SEsH2abf7cAX=BpLWExQ@mail.gmail.com> <op.v6k16ktpyzqh0k@pc-roelof> <033201ccbcab$5c5fe640$1502a8c0@Clemens04> <op.v6mtuugnyzqh0k@pc-roelof> <000901ccbcc4$42768fe0$c763afa0$@com> <4EECC1E8.4000806@iup.uni-heidelberg.de> <002c01ccbd6f$572761c0$0401a8c0@xphd97xgq27nyf> <39D91133A64A480596FBAA4395D85812@JimPC> <007901ccbd9e$69fe2ed0$0401a8c0@xphd97xgq27nyf> <008701ccbda1$cacf4f70$0401a8c0@xphd97xgq27nyf>
In-Reply-To: <008701ccbda1$cacf4f70$0401a8c0@xphd97xgq27nyf>
Subject: Re: LF: Re: Re: Re: Re: TX system at DK7FC, schematic
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Certainly not. What Stefan meant was the coil's *unloaded* Q, which 
cannot be high enough.

The *loaded* Q, in the resonant circuit, will be lower and that's what 
determines the antenna system's bandwidth.

Cheers,
    Wolf .

Am 18.12.2011 17:26, schrieb mal hamilton:
> ps
> With a Q in thousands the bandwidth even on 137 would be too narrow to be
> useful
>
> ----- Original Message -----
> From: "mal hamilton"<g3kevmal@talktalk.net>
> To:<rsgb_lf_group@blacksheep.org>
> Sent: Sunday, December 18, 2011 4:02 PM
> Subject: LF: Re: Re: Re: TX system at DK7FC, schematic
>
>
>> Jim es Co
>> The highest Q coils I have seen are self supporting encased in a helium
>> container and the Q specified was only in a few hundred. What sort of coil
>> construction yields 4000 and above ?
>> I have yet to encounter such a specimen
>> mal/g3kev
>>
>> ----- Original Message -----
>> From: "James Moritz"<james.moritz@btopenworld.com>
>> To:<rsgb_lf_group@blacksheep.org>
>> Sent: Sunday, December 18, 2011 10:58 AM
>> Subject: LF: Re: Re: TX system at DK7FC, schematic
>>
>>
>>> Dear Mal, LF Group,
>>>
>>>> I can see you resonate your 3mH coild with a motor driven variometer
> but
>>>> how
>>>> do you match this to exactly 50 ohmz for a SWR of 1:1 to the TX
>>>> I can see your coil and transformer secondary are  in series to earth
>> but
>>>> no
>>>> adjustment for matching.
>>> Essentially the same arrangement is in use here. The transformer ratio
> is
>>> adjusted to match the antenna resistance to 50ohms.
>>>
>>> A Q of 1000 is typical for a coil of this size wound using Litz wire.
> You
>>> might increase that somewhat by optimising length, diameter, winding
> pitch
>>> etc. For something big like the Balboa loading coil in Alex's mail, Q
> can
>> be
>>> considerably higher - Watt's "VLF Engineering" has data on this
> particular
>>> antenna system - the coil resistance at 25kHz is about 0.06ohms, and the
>>> reactance 225ohms, making the Q about 3800 - it might be higher at 136k,
>>> since reactance often increases faster than loss resistance as the
>> frequency
>>> goes up. Incidentally, I estimate L of the main loading coil about
> 1.3mH,
>> so
>>> GW0EZY would need the variometer in series as well ;-)
>>>
>>> Cheers, Jim Moritz
>>> 73 de M0BMU
>>>
>>>
>>
>
>
>