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ANTENTOP- 01- 2016 # 020

Modified Beverage Antenna

 

 

 

Table 4

 

Beverage Antenna with LDG Transformer Loaded to Bridge of 10 Wire Wound Resistors (overall resistance: 440 Ohm). Length of the 50- Ohm Coaxial Cable to antenna is 50’.  Measurement by MFJ- 259B

 

Band

160

80

40

30

20

17

15

12

10

Z

72@j8

59@j8

38@j7

78@j7

38@j7

79@j5

28@j35

113@j15

20@j13

SWR

1.4

1.2

1.3

1.5

1.3

1.8

1.7

2.2

2.5

 

 

 

SWR was not so bad with the new termination load made on the base of wire wound resistors. I tried the antenna directly connected to IC-718. I was again on the Air. Clean sound was at the 160 and 80- meter Bands. Contest stations begin answered to me. My station was restored.  However it was already 3.00- a.m. I went to sleep.

 

At the next day I decided change unsymmetrical RF Transformer that was used at my Beverage Antenna to transformer with insulated windings. At the times when I installed the Beverage Antenna I had no stuff to make the transformer with insulated windings.

 

However, at YORK REGION HAMFEST that was at 31- October, 2015, I bought butch of cables with ferrite ring on it.

 

 Seller did not have any information for the cables and for the rings on it. However it was a good price and box with the cables jumped to my backpack. At home I found that lots of the rings had inner diameter in ¼ inch that allows me make an RF transformer with insulated windings with standard copper ¼ inch tube (because the rings it was possible inserted on the ¼ inch tube).

 

So at the day before evening with Contest I decided make transformer with insulated windings. I expected that the transformer would provide better matching of the Beverage Antenna with coaxial cable. As well transformer with insulated windings should decrease the electrical noise level. Anyway if the transformer would not good I may use my old transformer made on the base of LDG Symmetrical Transformer. You may find lots design of such insulated RF transformer in the Internet.

 

Note: For example, link at ANTENTOP:

 

http://www.antentop.org/019/Two%20Broadband%20Symmetrical%20Transformers%20_019.htm

 

 

Figure 1 shows design of the transformer with insulated windings. For the transformer it was used 10 ferrite rings and two length of copper tube in ¼ inch OD. Photo shows kit for making the transformer. I should say that at making the transformer I met some unexpected problem. I had short length (6- cm) of ¼ inch copper tube. I could insert the rings on the tube. I had another one length of copper tube (1- meter length) but I cannot insert the rings on it. The diameter of the tube was a little wide.

 

Of course it would be possible to decrease the diameter with Dremel but… I took the ring and went to Home Depot. It was wonderful for me that among the rolls of copper tube in ¼ inch OD I may found tubes on which I may inserted the ferrite ring as well I may found ¼ inch tube on which I could not inserted the ring. So I took suitable tube roll with me.

 

 

Cable with Ferrite Ring on it

Note: At my job I did measurement the both copper tubes. Tube on which I may insert the ferrite rings had diameter in 0.248- 0.2495 inch.

Tube on which I could not insert the ferrite rings had diameter in 0.252- 0.255 inch. All dimensions were in the tolerance limits.

 

 

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April 2, 2016 22:49

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