wrote in message
ups.com...
Hi,

I am a new radio amateur from India (I got my license only a couple of
months back). My callsign is VU3RDD. This is my first experience with
Radio installation, so the questions and the problem I am facing may be
too silly and stupid. Neverthless... here it goes.

I live in an apartment on first floor. My inverted V for 40m and 20m
are on concrete terrace (of the 5 floor apartment). The mast is about
10 ft high. The ends of the dipole are not very symmetrically tied, as
the space constraints do not permit so. One of the ends of the dipole
is facing north and the other end towards west. Not exactly 90 degree
wide, but probably 100 to 120 degrees wide. The hight of the ends from
the terrace is not the same. I purchased a used rig last week and when
I measured the SWR, it sometimes hits 2:1, and sometimes more (if I
shout at the mic) for both 20m and 40m.

I have afew questions.

1. What are the ways to improve my antenna installation?

2. Does the concrete terrace act as ground for the antenna, and is 10
ft mast, just too short a height. The terrace itself is at around 50 ft
from the Ground.

3. I run a low loss RG213 coax from the terrace. Does the loss in the
cable contribute to the high SWR I am seeing?

Any other suggestions or general observations about this setup and hopw
I can improve the antenna setup? I also plan to learn NEC and simulate
this setup (hope it is possible to do it with NEC).

Thanks

73
Ramakrishnan, VU3RDD


Have you checked the SWR at different points in the bands? If you have what
differences have you measured. The antenna might just need tuned.. without
knowing how the difference between the top and bottom of the band it's hard
to say if anything else is affecting it.

Adair

Hi Adair,

I will try doing that. The said SWR is at around middle of 20m and 40 m
bands.

ramakrishnan

One more question:

While measuring the SWR, the needle fluctuates, as the voice is
modulated. Is the "value of SWR" the highest it hits? What's the
convention?

73
Ramakrishnan, vu3rdd

wrote:
While measuring the SWR, the needle fluctuates, as the voice is
modulated. Is the "value of SWR" the highest it hits? What's the
convention?

Depends on the inertial dampening of the meter needle.
If you can, use FM mode with zero modulation or simply
plug in a shorted audio plug to your CW key socket.
--
73, Cecil http://www.qsl.net/w5dxp

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wrote
While measuring the SWR, the needle fluctuates, as the voice is
modulated. Is the "value of SWR" the highest it hits? What's the
convention?
______________

Probably the ratio of forward to reflected power in your antenna system does
not change with the power applied to it. But many tx circuits that measure
SWR must be manually calibrated for the forward power in the system in order
for an ~ accurate indication of SWR.

The best accuracy is possible using CW output, after calibrating the SWR
meter for that forward power level. As the average power during voice
modulation usually is less than the rated average power capability of the
tx, the varying SWR readings you see when voice modulating might all be
lower than the true SWR of the antenna system.

RF

On 23 May 2005 04:49:08 -0700, "
wrote:
While measuring the SWR, the needle fluctuates, as the voice is
modulated. Is the "value of SWR" the highest it hits? What's the
convention?

Hi Ramakrishnan,

This is why you need to do it with CW, and why you need an external
meter/tuner. Building a meter is actually quite simple (although
recent correspondence here would contest that statement).

SWR should not vary. It is dependant upon the mismatch of the
transmitter to the load alone. When you get variations of SWR
readings depending upon signal strength, the problem is often an issue
of the meter, and then, secondarily, the transmitter's source
resistance. This is why you should tune at the level you are going to
transmit at. You can first get into the neighborhood with lower
levels while tuning (although you lack a tuner) and then boost to the
anticipated power for the last adjustment.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote
On 23 May 2005 04:49:08 -0700,
wrote:
While measuring the SWR, the needle fluctuates, as the voice is
modulated. Is the "value of SWR" the highest it hits? What's the
convention?

SWR should not vary. It is dependant upon the mismatch of the
transmitter to the load alone. When you get variations of SWR
readings depending upon signal strength, the problem is often an issue
of the meter, and then, secondarily, the transmitter's source
resistance.
_____________

'SWR meters' don't measure SWR directly. They sample the forward and
reflected signals, both of which vary during SSB voice modulation -- even
when the ratio between them (SWR) remains constant.

A variation in forward & reflected readings during SSB modulation is a
normal situation, and not necessarily traceable to the SWR meter, the tx
source Z, a varying antenna system Z, or anything else.

RF

I found from the manual that I can do CW with the Icom supplied mic.
Wanted to try it yesterday evening, but because of heavy wind and rain,
there was (is still) no power for the whole of yesterday night untill
now. Hopefully today evening I will try it out.

I am scared about transmitting, as costly stuff like a transceiver can
be difficult to get repaired in India. Sending it abroad for repair
costs as much as I would pay for a new transceiver!

73
Ramakrishnan, VU3RDD
http://www.hackGNU.org/

On 23 May 2005 21:15:25 -0700, "
wrote:

I found from the manual that I can do CW with the Icom supplied mic.
Wanted to try it yesterday evening, but because of heavy wind and rain,
there was (is still) no power for the whole of yesterday night untill
now. Hopefully today evening I will try it out.

I am scared about transmitting, as costly stuff like a transceiver can
be difficult to get repaired in India. Sending it abroad for repair
costs as much as I would pay for a new transceiver!

Hi Ramakrishnan,

And especially for such a small form factor. Most of the reviews I've
seen have been quite positive. The few negatives were about software.
However, I would point out that in regard to my last maxim about you
never building just one antenna; you never own just one rig. Get a
"beater" that you can get a soldering iron into without melting the
front panel at the same time. Maybe even one with (gasp) tubes. The
Ruskis are still building tubes, it seems, so at least surface
shipping shouldn't cost as much there.

Also, invest in a decent battery (car battery size) using your power
supply as a float charger. Then you can even out the power shortages.
In this case, however, a tube rig may be stretching the limits of a
battery. In that case, think of 20-25 year old transistor rigs (where
the ICs are TTL only). This stuff is easily field serviceable (I
know, because I've raised several from the dead).

This is all part of the "flexibility" you should plan on, as I also
mentioned before.

73's
Richard Clark, KB7QHC

Hi Richard,

Richard Clark wrote:
And especially for such a small form factor. Most of the reviews
I've
seen have been quite positive. The few negatives were about
software.
However, I would point out that in regard to my last maxim about you
never building just one antenna; you never own just one rig. Get a
"beater" that you can get a soldering iron into without melting the
front panel at the same time. Maybe even one with (gasp) tubes. The

Thanks for the suggestions. Yes, I think I am slowly learning the fact
that I should have multiple radios and antennas in hand.

Also, invest in a decent battery (car battery size) using your power
supply as a float charger. Then you can even out the power
shortages.

Ok..

In this case, however, a tube rig may be stretching the limits of a
battery. In that case, think of 20-25 year old transistor rigs
(where
the ICs are TTL only). This stuff is easily field serviceable (I
know, because I've raised several from the dead).

Ok.


This is all part of the "flexibility" you should plan on, as I also
mentioned before.

Ok. Thanks for all the suggestions. So, now I have to do quite a lot of
work to get back on air with a "decent SWR".

73
Ramakrishnan, VU3RDD