Topband: Core Mix Revisited

[Bert Barry]

>
>Mike(W5UC) & Kathy(K5MWH) wrote:
>>Let's assume we have four toroids of the same physical size, and 
>>there is one each of # 31, 43, 73, and 77 mix. Each is wound to 
>>isolate the coax, and each has a 5 turn primary and a 15 turn 
>>secondary. How does the performance of each differ and why?
>>
>>Hi Mike,
>>
>I won't waste bandwidth explaining why toroids and  5 turn primaries 
>are undesirable.  Others will do that.
>What I have to offer is the fact that 73 type toroids are not 
>marketed by anyone, as far as I know.  However, I once obtained four 
>of these that had been use for material evaluation purposes by the 
>manufacturer.  I wanted these for reflection transformers in 
>reversible beverages where the self impedance would have to be up in 
>the 2K region.  These worked OK, although they still required too 
>many turns for my liking.   When adding  more  Beverages, I switched 
>completely to binocular cores for the reflection transformers, as 
>well as the "near end" transformers.  To get the 2K plus impedance I 
>attached a pair of half-inch long binoculars together, end-to-end 
>with a couple of small droplets of crazy glue.  (There are one-inch 
>long binoculars available, but I was in a rush, and I had a large 
>stock of the half inch ones available).  These are much easier to 
>wind than toroids, as well as making more efficient use of the 
>ferrite material.
>
>I might point out that Amidon is not the only distributor of 
>ferrites, although it seems to be by far the best known to Hams.  I 
>have had very good service from CWS Bytemark.  I don't believe the 
>manufacturer, FairRite is too happy about filling small orders for Hams.
>
>Incidentally, I am surprised that many more people are not using 
>reversible Beverages.  My lot is long and narrow -  550 feet by 
>about 3000 feet, with the house near one corner, and reversible 
>Beverages are the only way I can cover 8 azimuths conveniently.  I 
>am in the process of adding phased Bevs (broadside-phased with 330 
>feet spacing for the short direction (550 feet), and end-fire feed 
>with the 850 foot-long ones aimed at Europe.
>If anyone else has had experience with phasing reversible Beverages, 
>perhaps with provision for varying the phase of end-fire 
>configuration,  I would be interested to hear their experience.
>
>Bert,  VE3QAA