Sensitivity is not always important. Small loops in general receive less
noise and the real exercise is balancing the internal noise floor
against the actual signal received. In some cases a loss up to 20 db can
be acceptable the numbers are easy enough to run.
On 6/16/12 8:17 PM, Brian Miller wrote:
> Hi Tim
>
> I also agree with the previous comments on this thread about detuning the
> transmit antenna (or any other wires/cables that are resonant on 160M) and
> isolating the coax feed line from the RX loop.
>
> It is also important to identify the direction of the main source of the
> noise and orientate the loop accordingly so that is being properly nulled. I
> use a small portable tuned loop to identify the direction of the noise..
>
> Of course, if the noise is coming from the same direction as the DX then you
> are not going to see much (or any ) improvement in the signal-to-noise
> ratio. Also, if the noise sources are in multiple directions then it will
> also be difficult to null the noise properly. I have found that small tuned
> loops (with their bidirectional nulls) are often more effective in such a
> situation.
>
> One of the problems with small tuned loops made from wire is their low
> sensitivity. Rather than using a pre-amp you can boost the output by making
> the loop larger (e.g., a circumference of 0.1 wavelength or even larger).
> The larger loop maintains a directional pattern similar to the smaller one
> but also exhibits a higher radiation radiation resistance and hence lower
> losses.
>
> Good luck with the experiments and let us know how you get on.
>
> 73, Brian VK3MI ZL1AZE
>
>> From: tshoppa@wmata.com
>> To: topband@contesting.com
>> Date: Sat, 16 Jun 2012 13:28:38 +0000
>> Subject: Topband: Receiving loops
>>
>> I want to try a new receiving antenna for the summer Stew Perry. Last
>> winter was my first foray onto 160M and I really felt like an alligator. I
>> could work everyone I could hear, with just 100W. I think that means I
>> need a better receive antenna. If you look at my score in the winter Stew
>> Perry I think I did great QSO-number wise, but my average distance was
>> very poor, I'm guessing typical alligator.
>>
>> I have tried pennants and K9AY's over the winter with little success.
>> Compared to my transmitting antenna (A "T" with a poor radial system) most
>> signals were still better, S/N wise, on my transmitting antenna. I feel
>> like I must've been doing something wrong. Still the fact that a few
>> signals came in on the loop with by ear much better S/N, maybe I was on
>> the right track and just didn't try hard enough.
>>
>> I will be trying a small tuned magnetic loop tonight (e.g. the last one at
>> http://www.w8ji.com/magnetic_receiving_loops.htm with the 9:1 transformer)
>> . And maybe a terminated beverage but I'm limited to about 150'... well
>> maybe I could run something longer down the driveway as long as I clean it
>> up before the sun comes up and the neighbors see.
>>
>> I was fairly impressed with small tuned magnetic loops when I was doing
>> some BCB DX'ing several years ago. I wasn't comparing with beverages or
>> anything.
>>
>> Tim N3QE
>> _______________________________________________
>> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
_______________________________________________
UR RST IS ... ... ..9 QSB QSB - hw? BK
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