开云体育

Top posting has some significant benefits.

Top posting is a courtesy to handicapped people. It is difficult, sometimes painful, for some folks to have to scroll down to the bottom of a long message, which everyone has already read, anyway, just to get to a reply - and many times the reply is short, like saying "I agree" or "right on" and so forth. Most folks can remember the thread without having to read it ever time there is a reply. It is often courteous to clip the original post just to give the drift of what one is trying to reply to, as it saves time, space, and bandwidth.

Just my take. /// Richards ///
==================================================

Len Warner wrote:

Hello

Do you and the other people interested in buying the AOR LA350 Loop Antenna have a PayPal Account, if not it is easy to register and it's free. Web address
www.paypal.com

One other thing postage would be extra and if required can be registered post or recorded delivery I think it's called. Hopefully this won't cost much.
Where do you live, I live in Letchworth Hertfordshire.

Thanks

Andrew.

Hi Andrew,

If you do decide to sell, I should be grateful for first refusal on
it.

Cheers

Fraser

--- In loopantennas@..., "aandrewb2001"
<andrew.lincoln2@...> wrote:

Hello all

I have a AOR LA350 Loop Antenna that I might be selling.
It is in mint condition, not sure if I have still got the manual or

not

but have got the box.
Comes with two loops and power adapter.
I would like ?70.00 for it if I decide to sell, is that reasonable?

Thanks

Andrew.

Hello all

I have a AOR LA350 Loop Antenna that I might be selling.
It is in mint condition, not sure if I have still got the manual or not
but have got the box.
Comes with two loops and power adapter.
I would like ?70.00 for it if I decide to sell, is that reasonable?

Thanks

Andrew.

If it a receive only antenna you'll probably be alright ... If you
need a little more capacitance you could parallel a fixed cap with a
trimmer ... the main drawback is you'll probably only have 20Khz of
bandwidth without making adjustments to the cap ... For a receive only
antenna you can always scrounge a polycon cap out of a cheap radio,
they usually run around 200pf and I've gotten several from radios for
a buck in a dollar-only store ... the ones I snagged were TRF AM
receivers with a TA7642 (ZN414 clone) TRF IC in a TO-92 package as
well as a small ferrite loopstick

If it's for transmitting you'll probably want to use a larger diameter
tubing and an air variable with fairly wide spacing or a vacuum
variable for high power

JR

--- In loopantennas@..., "l_atape" <l_atape@...> wrote:

Dear community,

I am searching for a simple solution for building a material-saving
magnetic loop for the 15 m HAM band.

If possible, I would like to use 0,8 cm flexible copper tube.

Unfortunately, I have just little 1 - 50 pf trimmer capacitors, not

more.

Is there any possibility to build a. m. antenna with the material
available?

Howdy Len and all,

There sure must be something different between the 31A and 31MS control boxes, I have not opened them up to see what it could be unless of course my 31A control box is faulty!

Trying the modified 31MS this morning 7:30 am our time (2030 UTC), the sun was already up and so the tropical bands had faded out, I started on 49 metres and found the Degen compared well to my outdoor antennas (yes, the 31MS is mounted inside my house), it was a mixed bag though on 41 metres and the Degen was getting noisier as time went on. All other bands from 31 metres up revealed the same symptoms as I had noticed yesterday during the early afternoon daylight hours, it was noisy as hell masking even moderate level signals that my other antennas could hear with ease, taking the loop and walking around inside my room as far as the cable would reach did not really show any improvements.

Is this loop antenna frightened of the sun or does the sun modify the angle that the signals are being received?

This afternoon, I then confirmed what I heard yesterday at around the same time, the Degen all of a sudden began to bring the signals in with more strength and less noise sometimes allowing a more readable audio on a weak signal than any of my other 3 outdoor antennas!

The thicker better quality cable I used between the control box and the loop terminating box was twin core shielded microphone cable using gold plated plugs (ah!! That's what made the difference, the gold plugs!!!)

The standard 31MS loop element could not even hear Vatican Radio compared to the solid core wire. The tuning peak become's broader and less peaky as the frequencies climb and this is with both loop elements (and is also true of my home built outdoor loop).

Something I did notice when trying out different variations when building my own loop, I tried varicap diodes and while fiddling with this large loop inside my room, signals were much noiser and weaker especially during the day compared to the large air tuning capacitor, this is what made me decide to not use varicap diodes (even though it would have made tuning simpler and easier!)

I also used the 31MS loop element and terminating box with the MW/SW switch and tried this Degen on Medium Wave. It gave fairly reasonable performance although I still noticed the noisier conditions over my wire antennas (my loop will only tune down to 2 MHz). Even turning the Degen to peak the signal did not reduce the noise and a lot of weak signals almost not registering on the "S" meter that had quite readable audio with my two outdoor wires were totally masked by the Degen as if they were not even there!

So, this is a weird antenna in that it does not like daytime signals, night time allows the 31MS to shine through but come day, it is like an owl, goes to sleep and put's up a shield of noise!!

At least I am happy that it does perform so well during the late afternoon until the early hours of the morning, it will become my 4th antenna for night listening while I shall have to put up using my 3 outdoor antennas for the daytime DX!

Best wishes from a hot and humid down under!

Michael S

Michael, thanks for a most interesting comparison.
I won't quote the whole of it in my reply [ hint, hint ;-) ]

At 3:10 am ((PST)) Sat Feb 10, 2007, Stevenson wrote:

[big snips throughout]
The 31A is a fair performer only and it's limiting factor is the tuning box,
using the 31MS tuning box with the 31A loop all other things equal
improves the loop's performance quite a lot. The 31MS provides more gain
and signal to noise ratio most of the time depending on the received signals.

This performance difference is intriguing. According to the
DRM Software Radio Forums thread, the DE31 (not DE31-A)
control box contains only an L-C DC power injector in the
signal path, the rest is power supplies for the loop amplifier
and varactor tuning bias.

So what is different in the MS control? Perhaps it is a
matching transformer, perhaps it is a buffer amp or the
"top half" of a cascode pair. Perhaps it is time for Fraser
to take a screwdriver and camera to his TG34 again ;-).

Both loops fair rather poorly during the daylight hours with high
noise levels masking weak and some moderate signal levels.

Do you get the impression that this is due to poor performance
of the Degen loops on weak signals or to the different noise
environment of indoor and outdoor antennas being revealed by
lower daytime signal levels?

(I'm assuming the Degen loops were used indoors near the
receiver - but perhaps you literally have a "shack" outside.)

Using a thicker higher quality and shorter cable between the control box
[and ]the loop element resulted in even better performance and noise figures.

What kind of cable was this? I presume the original is a
lightweight screened twin, one core carrying signal+power
and the other the tuning voltage. I wondered if it might be
better to use a independently screened twin in case the
tuning conductor couples in some losses.

Replacing the origional soft cord loop element with much stiffer 1mm motor
rewind wire of a similiar diameter resulted in yet another improvement in
signal and noise although only slight (but it all adds up and helps right?)

Nice to know 1mm is thick enough to make a noticeable
difference. So the "bell wire" twin I have ought to give similar
or better performance (wires paralleled) and be flexible too.

In standard form, both loops are quite directional especially during
the daylight hours but a little less so when signals are strong

This could be an effect of receiver AGC rather than the loop.
When the signal is strong the AGC action appears to narrow
the angle of the null by compressing the amplitude variation.

This effect is very noticeable when using a domestic receiver
for MW DX - the null can be very difficult to find except by
listening for increased background noise as the gain is wound
up to level the signal. You do notice the null in a weak station
if a nearby strong signal is pinning the AGC level - which is
good for direction finding but the opposite of what is wanted
for DX listening.

although you can quite affectively

Yes, I really _loathe_ it! ;-)

null out some QRM provided
it is coming from a different direction around 90 degrees.

Which may be an example of the AGC effect last mentioned.

Come 0525 UTC (4:25 pm local summer time), with the DE31MS control
box on the 31A Loop box with the motor wire in place and the short thick
cable coupling the loop to the control box, I was amazed to hear a weak
and noisy Vatican Radio's ID signal for closing down at 0530

How does the straight DE31MS loop compare to this hybrid?

Of course, the Degen tends to be a little band fussy with observations noted:
49 [snip through to]13 metres held it's own against all other antennas

Did you still detect a loop tuning peak at the upper frequency?
I.e. could you tune through the peak or were you only climbing
up the lower frequency slope? The 22MHz end of the range
demands a very low tuning capacitance, lower than the varicap
is specified to at 8V. I would be interested to hear what the
result of squashing the loop into a narrower diamond would be.

This would decrease the inductance (and the sensitivity) but
allow tuning across the peak - or the tuning control could be
set at maximum and the loop tuned by varying the width,
either way ensuring the loop is actually at resonance at
the maximum frequency required.

I will be doing further tests and experiments and hope to mount the loop
on a thin mast for better support and for rotating easier. Any suggestions
of what I should use for the mast material?

I have a collapsible fibreglass fishing rod for portable use
but I notice the garden season has arrived in the shops
so I shall be looking for a fibreglass garden stake, or a
bamboo stake would do - anything non-conductive, on top
of a metal mast for height if necessary.


Regards, LenW

Dear community,

I am searching for a simple solution for building a material-saving
magnetic loop for the 15 m HAM band.

If possible, I would like to use 0,8 cm flexible copper tube.

Unfortunately, I have just little 1 - 50 pf trimmer capacitors, not more.

Is there any possibility to build a. m. antenna with the material
available?

Once Again , The knowledge that's shared out here is amazing ! I like
to listen to the AM (MW) Band . I enjoy digging DX out from under our
50KW Blowtorches ! I generally use an amplified whip (or "short-
wire") phased against a loop antenna-- usually also amplified !
I'ved had good luck with the the Select-a-tenna , Although the signal
doesn't compare to the KIWA LOOP which I've used before . I'm really
surprised that know one has has released a newer version of the KIXA
Antenna ! Anyway -- THANKS AGAIN !
__LESTER THANKS AGAIN -- In loopantennas@..., "Fraser"
<fraser.castle@...> wrote:

Sorry I can't compare the DE31MS to th eloops that you have

specified

as I do not own them I can, however state the following -

The Degen loops are cheap and cheerful, They are not the best made
units but are good value for money if portability is desired.

I have compared my DE31 to a Sony AN-LP1 and an AOR LA320. In both
cases it produced inferior signals. You do tend to get what you pay
for with these commercial active loops but no one can argue with

the

value for money (VFM) aspect of the Degen series. I probably

couldn't

build such an active loop for the price I paid (DE31 $16 delivered
from China).

I consider the Degen loops to be a useful addition to my loop

arsenal

for portable work but they are not the best in my collection by a
long way.

It is interesting to note that the Sony LP1 also uses a single turn
loop and unbalanced FET amplifier. It's performance is excellent so
it would appear that the Sony uses a better pre-amplifier design.

Regards

Fraser

Howdy folks,
I have spent all afternoon playing with the Degen DE-31A and the DE-31MS and I have had lot's of fun as well as some surprises!!

Reference antennas are PAR Electronics EF-SWL wire with balun, my own 55 foot wire with balun and my own 1.4 metre diameter 3/4 inch copper tubing loop with large air spaced tuning capacitor at the top with a 1/5 th sized Faraday shield coupling loop at the bottom into a pre-amp (MPS-102 FET and Transistor driver). It sits on top of mast with rotator and is remotely tuned with motor drive on the tuning capacitor from controls in my DX shack, the loop is mounted 8 foot from the ground in the middle of my backyard and all cables are run underground!

Receivers used are an Eton E1, Drake SW-8 and Redsun RP-2100 and antenna switching is provided by a 6 port LDG Electronics relay switch box.

The 31A is a fair performer only and it's limiting factor is the tuning box, using the 31MS tuning box with the 31A loop all other things equal improves the loop's performance quite a lot. The 31MS provides more gain and signal to noise ratio most of the time depending on the received signals. Both loops fair rather poorly during the daylight hours with high noise levels masking weak and some moderate signal levels.

As a comparison of daytime signals, all three of my other antennas had much higher signal levels and superior signal to noise ratios resulting in fair to good reception of weak fading signals. During daytime, the 31A had far less signal but a slightly better noise figure on some signals and by switching in the E1's pre-amp, it helped quite a lot!

As the afternoon dragged by and the lower bands begin to open up a little more, the 31MS seemed to improve considerably leaving the 31A for dead. Using a thicker higher quality and shorter cable between the control box the loop element resulted in even better performance and noise figures. Replacing the origional soft cord loop element with much stiffer 1mm motor rewind wire of a similiar diameter resulted in yet another improvement in signal and noise although only slight (but it all adds up and helps right?)

In standard form, both loops are quite directional especially during the daylight hours but a little less so when signals are strong although you can quite affectively null out some QRM provided it is coming from a different direction around 90 degrees.

I have to say that the Degens performed similiar on all 3 radios although the Drake was happy with all antennas tested while the E1 and RP-2100 exhibited far greater differences between the antennas!

Come 0525 UTC (4:25 pm local summer time), with the DE31MS control box on the 31A Loop box with the motor wire in place and the short thick cable coupling the loop to the control box, I was amazed to hear a weak and noisy Vatican Radio's ID signal for closing down at 0530, I could understand the signal and identify the station (with all 3 receivers) while all other antennas eccept for the EF-SWL wire could not even hear it. Other signals coming in showed a consistant equal or better performance for signal strength and noise than any of the other antennas including my own outdoor loop! I am amazed and surprised and this is all with the antenna sitting inside about 7 foot off the floor close to the ceiling with a 3 foot thicker cable connecting it to the control box and I wasn't even rotating it to see what would happen (that will come next!).

Of course, the Degen tends to be a little band fussy with observations noted:
49 metres good all round
41 metres excells or equals
31 excells or equals most stations
25 metres excells most of the time with my large outdoor loop 2nd!
22 metres a mixed bag with some good and some not so good, maybe rotating would help on the weaker noisier signals!
19 & 16 metres are mixed bags
13 metres held it's own against all other antennas (eccept my loop which only tunes up to 16 metres!)
I have not had a chance to listen to the tropical bands due to still daylight hours and heaps of local thunderstorms creating nothing but static on all antennas!

I will be doing further tests and experiments and hope to mount the loop on a thin mast for better support and for rotating easier. Any suggestions of what I should use for the mast material?

The experiments and modifications are certainly worthwhile but I have to do more daytime listening to determine if these degens are for afternoon, night and morning listening only and not so good for midday DX!

Best wishes from down under!

Michael S

Howdy,

I have found following indepth experiments today that the Degen DE31MS has a far superior tuning box compared to the standard 31, the MS version has better gain and slightly better signal to noise ratio which in some cases compares to or beats my outdoor antennas, see my later post coming up today!

Best to all!

Michael S

Sorry I can't compare the DE31MS to th eloops that you have specified
as I do not own them I can, however state the following -

The Degen loops are cheap and cheerful, They are not the best made
units but are good value for money if portability is desired.

I have compared my DE31 to a Sony AN-LP1 and an AOR LA320. In both
cases it produced inferior signals. You do tend to get what you pay
for with these commercial active loops but no one can argue with the
value for money (VFM) aspect of the Degen series. I probably couldn't
build such an active loop for the price I paid (DE31 $16 delivered
from China).

I consider the Degen loops to be a useful addition to my loop arsenal
for portable work but they are not the best in my collection by a
long way.

It is interesting to note that the Sony LP1 also uses a single turn
loop and unbalanced FET amplifier. It's performance is excellent so
it would appear that the Sony uses a better pre-amplifier design.

Regards

Fraser

Hi Len,

I have uploaded a picture of the TG33 loop head unit for you.

You can find it n the photos area under TG33 loop.

As you will see, the TG33 MW loop uses an inductor in much the same
way as the TG34/DE31MS except this one is red in colour.
The TG33 uses a single turn loop construction (the cores are soldered
together to increase the cross section).

Regards

Fraser

Thanks for the reply. I decided to map my property today and found
that I have 4 trees not quite at 40' and not real square but will do
the job and it shortens my feedline run. Now all I need is warmer
weather.

73's Bob
KB1DIA

--- In loopantennas@..., john nelson <jnelson123_us@...>
wrote:

I talked to a guy in New Mexico who had a large
horizonal loop that he put up at 20' using 2 sections
of conduit. It was working very well which leads me
to believe that the metal poles are not a problem.

John N.
KE5FRY
--- "Bob B." <rgb98rstd@...> wrote:

Hi

I am in the process of getting materials for an
80-10 Loop Skywire. I
plan on setting this up in a Hex Shape to gain as
much "Maximum
Enclosed Area". I was wondering if metal supports
could be used for
this type of antenna? Also should the antenna be
level (as much as
possible) or can it slope? The ground where I plan
to set this up has
a 4-5 ft slope to it.

Any info would be appreciated.

73's

Bob

____________________________________________________________________________________

Looking for earth-friendly autos?
Browse Top Cars by "Green Rating" at Yahoo! Autos' Green Center.

It would be interesting to know if anyone on the list could model
that on EZNEC. I've just got to learn to use that program someday!
Dave


--- In loopantennas@..., john nelson <jnelson123_us@...>
wrote:

I talked to a guy in New Mexico who had a large
horizonal loop that he put up at 20' using 2 sections
of conduit. It was working very well which leads me
to believe that the metal poles are not a problem.

John N.
KE5FRY
--- "Bob B." <rgb98rstd@...> wrote:

Hi

I am in the process of getting materials for an
80-10 Loop Skywire. I
plan on setting this up in a Hex Shape to gain as
much "Maximum
Enclosed Area". I was wondering if metal supports
could be used for
this type of antenna? Also should the antenna be
level (as much as
possible) or can it slope? The ground where I plan
to set this up has
a 4-5 ft slope to it.

Any info would be appreciated.

73's

Bob

____________________________________________________________________________________

Looking for earth-friendly autos?
Browse Top Cars by "Green Rating" at Yahoo! Autos' Green Center.

I talked to a guy in New Mexico who had a large
horizonal loop that he put up at 20' using 2 sections
of conduit. It was working very well which leads me
to believe that the metal poles are not a problem.

John N.
KE5FRY
--- "Bob B." <rgb98rstd@...> wrote:

Hi

I am in the process of getting materials for an
80-10 Loop Skywire. I
plan on setting this up in a Hex Shape to gain as
much "Maximum
Enclosed Area". I was wondering if metal supports
could be used for
this type of antenna? Also should the antenna be
level (as much as
possible) or can it slope? The ground where I plan
to set this up has
a 4-5 ft slope to it.

Any info would be appreciated.

73's

Bob

____________________________________________________________________________________
Looking for earth-friendly autos?
Browse Top Cars by "Green Rating" at Yahoo! Autos' Green Center.

--- In loopantennas@..., Len Warner <novost@...> wrote:

At 12:03 am ((PST)) Thu Feb 8, 2007, Fraser wrote:

Please see my post on the internals of the DE31MS loop head.

Thanks for your excellent efforts, Fraser. I shall
download the picture in a moment... got it :-)

Do you know if the TG33 MW-only loop is
single-turn plus a series inductor too?

Sorry if I appeared to ignore or contradict your
earlier post: I receive the Digest, so I'm just
playing catch-up now.

I had overlooked the possibility of inductance in
series with the loop. Which is most remiss of
me, since I was recently looking at the reference
design for a receiver chip which used the same
technique to switch the ferrite rod aerial from
MW to LW. So no excuses ;-).

As you say, not the most efficient, however...
...I happen to have been looking at several
band-pass filter designs and one suggested
a Q of 30 for commercial bobbin-cored inductors
vs 100 for hand-wound ferrite toroids - and both
gave acceptable insertion loss in an aerial
preselector.

[On the other hand, I have seen bobbin inductors
condemned as having much lower Q, down into
single figures, so I guess "it all depends" - on the
method of measurement, too :-(.]

I suspect much better than 100 is possible with
a carefully sized and wound toroid. Alternatively,
Q in the region of 1000 is possible in an air-cored
solenoid - making a good padding coil for a fixed
location but rather poor luggage.

For a tuned loop a Q of 30 is a bit low but 100 is
quite reasonable. Remember that the higher the Q,
the more often a SWL will have to re-tune the aerial
while searching HF, at high Q it becomes tricky to
peak the loop on the receiver frequency and audio
sidebands can be clipped, and at extreme Q CW
signals will ring - and the tuning drift will probably
make it unusable.

Some designs include a switched or variable
Q-spoiler resistor across the tuned circuit to make
the loop more friendly to operate.

Better to have spare performance in hand (and
then be able to discard some) than be found
wanting, but no need to chase the ultimate and
find it unusable.

BTW, for those tempted to rebuild their loop,
be mindful that the cute little low-capacitance
mosfet has no internal gate static protection,
so a permanent RL shunt across the loop
terminals in case the external loop should
ever be disconnected could be a good idea.


Regards, LenW
I'm seeing alot of buzz about this new loop . How does this loop

compare to the Quantum Loop (Gerry Thomas) , or the now defunct Kiwa
Loop ? Also-- Does PHASING work as well on shortwave , as it does on
MW ? I do alot of phasing of 2 antennas to get sharp nulls ,
sometimes with unbelievable results ! ---Lester J Kleidon--

starayzzz schreef:

I untied the knots, desoldered one connector and slipped off that
telescoping element when I got my DE31, so I have no baseline, [I've
never seen a quadratic element with such a diagonal across it before
and assumed the telescope to be an engineering/marketing compromise]
I'm using #4 straws with a broken fishing rod tip inside... what I do
notice is directivity when the ant is a few feet within the window,
this is most evident when adjusting/rotating the ant to best receive
DRM signals...

The best radio to see directivity is the Sony 2001D ...

Other rdio's aren't that good on signal meters..

(I have lots of analogue radio's... and a panasonix 65rfd)

Marc

Thanks for the suggestion Steve, yes, I will do a number of tests and comparisons, it will be interesting and fun!

Best wishes!

Michael S

At 12:03 am ((PST)) Thu Feb 8, 2007, Fraser wrote:

Please see my post on the internals of the DE31MS loop head.

Thanks for your excellent efforts, Fraser. I shall
download the picture in a moment... got it :-)

Do you know if the TG33 MW-only loop is
single-turn plus a series inductor too?

Sorry if I appeared to ignore or contradict your
earlier post: I receive the Digest, so I'm just
playing catch-up now.

I had overlooked the possibility of inductance in
series with the loop. Which is most remiss of
me, since I was recently looking at the reference
design for a receiver chip which used the same
technique to switch the ferrite rod aerial from
MW to LW. So no excuses ;-).

As you say, not the most efficient, however...
...I happen to have been looking at several
band-pass filter designs and one suggested
a Q of 30 for commercial bobbin-cored inductors
vs 100 for hand-wound ferrite toroids - and both
gave acceptable insertion loss in an aerial
preselector.

[On the other hand, I have seen bobbin inductors
condemned as having much lower Q, down into
single figures, so I guess "it all depends" - on the
method of measurement, too :-(.]

I suspect much better than 100 is possible with
a carefully sized and wound toroid. Alternatively,
Q in the region of 1000 is possible in an air-cored
solenoid - making a good padding coil for a fixed
location but rather poor luggage.

For a tuned loop a Q of 30 is a bit low but 100 is
quite reasonable. Remember that the higher the Q,
the more often a SWL will have to re-tune the aerial
while searching HF, at high Q it becomes tricky to
peak the loop on the receiver frequency and audio
sidebands can be clipped, and at extreme Q CW
signals will ring - and the tuning drift will probably
make it unusable.

Some designs include a switched or variable
Q-spoiler resistor across the tuned circuit to make
the loop more friendly to operate.

Better to have spare performance in hand (and
then be able to discard some) than be found
wanting, but no need to chase the ultimate and
find it unusable.

BTW, for those tempted to rebuild their loop,
be mindful that the cute little low-capacitance
mosfet has no internal gate static protection,
so a permanent RL shunt across the loop
terminals in case the external loop should
ever be disconnected could be a good idea.


Regards, LenW