Topband: Ferrite Cores

[Carl]

> On 8/6/2014 8:31 AM, Carl wrote:
>> 31 and 43 mix are the popular ones in the 2-30 MHz range for common mode 
>> suppression; 31 wins at 160 and 80, but 43 is better in the 7-30 range.
>
> I would amend that only to say that #31 and #43 are roughly equivalent in 
> the 5-15 MHz, range, #43 is slightly better above 15 MHz.  #43 is a bit 
> less expensive than #31, but the cost difference disappears if you buy #31 
> in quantity.  My last group purchase of #31 2.4-in cores was for 1,100 
> pieces, about two years ago. We paid about $4.
>
> Because #31 is so much better on 80 and 160, because it is more broadband 
> below 15 MHz, and because it remains effective through the HF range, I 
> long ago made the engineering decision to buy #31 in quantity for ham HF 
> applications.  If I were ONLY working above 80M, I would look at pricing 
> on #43 in the quantities I needed.
>
> 73, Jim K9YC


Im just basing it on some personal experience but havent run any lab tests.

On a 40M inverted V with apex at 55' Id been using a pigtail with 43 for 
years, switching to 31, and no ferrite I couldnt hear any difference, both 
worked well. I mentioned the 43 since it is much cheaper.

For 20M I used a 3 el HB monobander at 60' on another tower and the 43 
seemed a hair better.

Not exactly scientific and with a wide range of mix tolerances Im not going 
to worry about it, a few extra turns of coax would have sufficed.

Both antennas are part of the AM station and were easy to get to.

Since I dont run enough power to cause non linearities that isnt a concern 
on TX.

Carl
KM1H