[Elecraft] KX3 tuner loss?

[Ron D'Eau Claire]

FB. I get enough e-mail already. Hope your questions were answered. 

73, Ron AC7AC

-----Original Message-----
From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Barry
N1EU
Sent: Thursday, November 3, 2016 2:35 PM
To: Ron D'Eau Claire
Cc: elecraft
Subject: Re: [Elecraft] KX3 tuner loss?

It ends up that John KN5L gave a thorough treatment to the topic in this
thread (might need to be a member of the KX3 Yahoo Group to read):
https://groups.yahoo.com/neo/groups/KX3/conversations/topics/5869

73, Barry N1EU

On Thu, Nov 3, 2016 at 4:08 PM, Ron D'Eau Claire <ron at cobi.biz> wrote:

> You ask a commonly asked question. And, as usual, no responses so far.
>
> I can't give you an estimate either because first, the losses are 
> highly dependent upon the impedance transformation. You'd need to 
> characterize that doublet and feed line (the length of the feed line 
> is important) to see what impedance it presents to the ATU.
>
> Then you need to measure the ohmic losses in the ATU inductors, wiring 
> and connectors. Dielectric losses may occur but with modern gear they 
> are very tiny at HF.
>
> Finally you calculate the currents flowing in the ATU at each 
> impedance transformation required to achieve a match to your feed line 
> so you can calculate the losses based on the resistance of the wires, 
> inductors, and connectors.
>
> Personally, I accept the idea that an L-network (which all the 
> Elecraft ATUs
> use) is highly efficient and leave it at that.
>
> If I were really inclined to actually measure the loss, I'd first 
> measure the RF power output into a stable 50 ohm load without the ATU 
> in the circuit. Measure with an external wattmeter at the load as well 
> as the KX3 output power indicated.
>
> Then I'd breadboard another L-network with a variable cap and variable 
> inductor, connect it to the 50 ohm load and to the KX3 output, 
> transmit and adjust the external L-net (not the KX3 ATU) for a 1:1 
> match. In that way you have created a known dummy load that presents 
> the same complex impedance to the KX3 as your antenna system.
>
> Now you can transmit at the same power at the KX3 as before and see 
> what the power is at the 50 ohm load. Actually, you will be seeing 
> what the power is after passing through both matching networks.
>
> My guess is that you'd find the total loss so low you won't be able to 
> read the difference on the two power meters.
>
> A more direct approach would be to isolate the ATU in a very well 
> insulated enclosure, transmit, and measure the temperature rise until it
stabilizes.
> You can then calculate how much energy is being dissipated by the ATU 
> and becoming heat. That requires the ATU be carefully isolated from 
> the rest of the KX3 and be in a very well insulated enclosure to avoid 
> loss of heat to the environment, something not practical to do with a 
> KX3. It is, however, a valid way to determine losses in external 
> devices like an RF transformer (e.g. "balun").
>
> I suspect this explains why few (if any) Hams bother to make the 
> measurements.
>
> 73, Ron AC7AC
>
>
>
>
>
> -----Original Message-----
> From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of 
> Barry N1EU
> Sent: Thursday, November 3, 2016 7:20 AM
> To: elecraft; KX3 at yahoogroups.com
> Subject: [Elecraft] KX3 tuner loss?
>
> I'd appreciate knowledgeable estimates of the loss in dB through the 
> KX3 ATU when working into a 44ft (NorCal) doublet fed with twinlead, 
> with or without a BL2 balun inline, on 20/17/15M.
>
> Thanks & 73,
> Barry N1EU
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net Please help support this email 
> list: http://www.qsl.net/donate.html Message delivered to ron at cobi.biz
>
>
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html Message
delivered to ron at elecraft.com