Usually, in a T tuner, more inductance is lower loss from lower loaded Q
and so greater bandwidth. Usually lower inductance means a higher loaded
Q, greater circulating currents, and so greater loss and narrower
bandwidth. In an L tuner there is only one set of values that will make
a match. The Q is higher the greater the impedance transformation ratio.
And there's nothing you can do in the tuner to get around that. But
changing the feed line length or impedance to get an impedance easier to
match can achieve that. Also sometimes you can use external C or L
across or in series with the feedline to tune out the worst of the
reactance to make life easier for the tuner. That, like adding feedline,
tends to be band specific.
73, Jerry, K0CQ
On 2/15/2011 12:07 PM, Rick - NJ0IP / DJ0IP wrote:
> Tom,
>
> You should be able to tune the entire band, no problem.
> You may have to add (or cut off) another 2 ft. of feedline.
>
> Tuning can sometimes be very critical.
> I put bigger knobs on my 974 matchbox so that I had a better "fine feeling"
> when tuning.
>
> I believe if you change the inductance, either one notch up or down, and
> fine tune, you will probably be able to get a low SWR over the entire band,
> as is, without any further pruning. If not, prune a bit more.
>
> 73
> Rick
>
> -----Original Message-----
> From: tentec-bounces@contesting.com [mailto:tentec-bounces@contesting.com]
> On Behalf Of tom stewart
> Sent: Monday, February 14, 2011 11:22 PM
> To: Discussion of Ten-Tec Equipment
> Subject: Re: [TenTec] Antenna follow up- asked for help in January- need
> more help.....
>
> This did in fact work well for me tonight. The bands are not great tonight
> so I did not make any contacts but at least I can tune up on 7,10,14 and
> 18mhz. It is a little touchy on 40 as it dips at 7.5 but it is OK at 7.025.
> The resistance is around 600 and the reactance is near zero. In fact all
> those bands have a similiar result- high resistance and low reactance- that
> is OK I think. It is resonant on 18.068 which is cool. I have made many DX
> contacts on 18
>
> Thanks for your help- Tom N7ESE
>
> ..On Mon, Feb 14, 2011 at 3:40 AM, Rick - NJ0IP / DJ0IP
> <Rick@dj0ip.de>wrote:
>
>> Tom,
>>
>> Here is a probable fix for 40m.
>>
>> If you have any of the commercial 450 ohm ladderline, use it and add 13
> ft.
>> of line to the antenna.
>> I assume you can run it inside your shack, which is why I say to use
>> commercial stuff (easier to work with and zigzag back and forth than the
>> home made stuff).
>>
>> If you don't have commercial ladderline, then add about 15 (or 14 ft.) of
>> your homebrew openwire to the feedline.
>>
>> The trick is to add an electrical 1/8 wavelength.
>> I don't know the velocity factor of your home brew line, that's why I
> can't
>> say the exact length but it will be about 14 or 15 ft, maybe even 16 ft.
>>
>> I'm pretty sure that will fix 40m, and probably 30m as well.
>>
>> MOST LIKELY, THE ONLY PROBLEM YOU ARE HAVING IS THAT YOU HAPPENED TO HIT A
>> VERY UNPRACTIVAL TOTAL LENGTH OF ANTENNA PLUS FEEDLINE!
>>
>> I use the same antenna with the same matchbox (I have the MFJ-974B) and it
>> produces a very good match on ALL bands, from 80 thru 10, but I have a
>> longer feedline, whose length I have not measured. It runs exactly from
>> the
>> antenna to the shack, and I got lucky!
>>
>> 73
>> Rick
>>
>>
>>
>>
>>
>> -----Original Message-----
>> From: tentec-bounces@contesting.com [mailto:tentec-bounces@contesting.com]
>> On Behalf Of tom stewart
>> Sent: Sunday, February 13, 2011 7:17 PM
>> To: TenTec@contesting.com
>> Subject: [TenTec] Antenna follow up- asked for help in January- need more
>> help.....
>>
>> OK,
>>
>> Many came to my aid when I asked for suggestions. I made some choices and
>> built an antenna. I tried hard to maintain spacing and avoid metal by at
>> least a foot. It did not come out well so I need help. Here are the
> details
>> if anyone has some suggestions I would be grateful-again.
>>
>> 1. Purchase "Ladder Snap" spreaders to build 600 ohm feeder.
>>
>> 2. Purchased plenty of 14 gauge THHN wire.
>>
>> 3. Because of room constraints, the legs of my inverted Vee are 31 feet.
>> Center is 35 feet high and the legs end at about twenty feet.
>>
>> 4. Legs to feeder is continuous- feeder is 45 feet from center and
>> terminated by grounded shield coax through window pane(vinyl).
>>
>> 5. Tuner is for now an MFJ balanced- model 974-I think.
>>
>> 6. reactance is high on all bands. It will only tune up on 14MHZ. tuner
>> arcs if I persist at 7mhz
>>
>> 7. readings with antenna analyzer are as follows:
>>
>> Readings are at the bottom of the bands beacause I operate CW only.
>>
>> 7.020mhz r57 x158 swr 10.0
>>
>> 10.110mhz r168 x 135 swr 6.0
>>
>> 14.020 r21 x58 swr 7.5
>>
>> 18.075 r20 x70 swr9.1
>>
>> Thanks in advance- I know it is difficult to say with this limited
>> information but I am at my wits end- about 10 hours into this
>>
>>
>> Tom N7ESE
>> _______________________________________________
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>> TenTec@contesting.com
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>>
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>>
>
>
>
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