The actual difference will vary somewhat depending on where the bend
is. The simple one I tried had only one degree difference, 25 and 26
degrees, but the difference between the two elevations was only ONE
TENTH of a dB between the two elevations on either pattern. What this
means is that the difference will never be heard by the operator on
the other end of the QSO.
On the other hand, poor treatment of ground issues has resulted in
measured losses more than enough to swallow up the gain of a QRO amp
like it was turned off.
On 160 meters the name of the game is how to avoid direct or induced
ground losses. Worry about wire shape when you are sure your ground
losses are factually restricted to the unavoidable in your situation.
Have a look at the sources of loss below and around your antenna.
Make a list of things you can do reduce direct or induced ground
losses. Do those. Run the inverted L any way you can consistent with
minimizing ground losses. Some horizontally polarized radiation may
be useful in that situation. Low angle vertical radiation does not do
well going through buildings. Count those as ground losses over which
you have no control.
73, Guy.
On Tue, Jul 27, 2010 at 10:47 AM, tzikas tzik <tzitzikas77@gmail.com> wrote:
> hi. thank you for your answer. What elevation angle has the 5/16 inverted L
> and what elevation angle has the 1/4? Must i will reduce the total lenght
> from 5/16 to 1/4 for higher local signal or the difference is just a little
> bit, and to keep the 5/16 inverted L? If i keep the 5/16 inverted L what i
> must change to increase the signal? Now i am using 6 radials (4 1/8 and 2
> 1/4).which are constructed with insulated wire and are placed on the ground.
> Moreover, what do you think about T antenna?
> My transmitting area is like this draw:
> http://tzitzikas.webs.com/transmitter_area.JPG
> In the front of transmitter's house, there is a third building with 6
> floors. So, the vertical portion of my antenna is found between 3 buildings.
> I think it is a problem for the signal transmittion. What do you propose?
> Now, for match system with my 50ohm transmitter, i am using a variable
> series capacitor (0-500pf).
>
> On Mon, Jul 26, 2010 at 11:11 PM, Guy Olinger K2AV <olinger@bellsouth.net>
> wrote:
>>
>> There is very little difference in the pattern of a 5/16 inverted L
>> and 1/4 inverted L that has the bend to horizontal at the same height,
>> assuming a bend even roughly half way. The lower the bend the higher
>> the maximum lobe takeoff, but it's a mild change. 29 degrees vs. 49
>> degrees is not correct, all other issues held constant.
>>
>> 73, Guy.
>>
>> On Sun, Jul 25, 2010 at 11:49 AM, tzikas tzik <tzitzikas77@gmail.com>
>> wrote:
>> > Hi. I have a transmitter for 160m band about 200-300w r.f output power.
>> > Now
>> > i am using an (5/16)X(wave length) inverted L. I am looking for an
>> > antenna
>> > which will provide strong local signal. I have read that the 5/16
>> > inverted L
>> > has about 49o elevation angle and the 1/4 inverted L has about 26o
>> > elevation
>> > angle. So, i think that 1/4 inverted L, provide more strong local
>> > signal.
>> > what do you think about this?
>> > Now with 5/16 inverted L it very easy to match it with the 50ohm
>> > transmitter
>> > by using only a series variable capacitor. I am afraid that with 1/4
>> > inverted L it will be more difficult to match it with the transmitter.
>> > What
>> > i need (coils and capacitors) to match it? thank you very much
>> > _______________________________________________
>> > UR RST IS ... ... ..9 QSB QSB - hw? BK
>> >
>
>
_______________________________________________
UR RST IS ... ... ..9 QSB QSB - hw? BK
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