| CHOKING BALUN FOR LOW BAND VHF Choking balun for upper HF to lower VHF bands. (10MHz - 60MHz). Requiring a choking balun to isolate the potential common mode RF on the coax cable for a new 6m band Ringo antenna. 
Figure 1 Schematic of the 1:1 choking balun | Type | Choking Balun | | Ratio | 1:1 | | Frequency Range | 14 ~ 54MHz | | Choking Impedance | 2k Ohms minimum. Ref: Figure 3 | | Core Used | FT140-43 Ferrite Toroid Core | | Number of turns | 8 (4 + 4). Ref: Figure 2 | | SWR | 1:1 Ref: Figure 4 | 
Figure 2 Winding details of the 1:1 choking balun Construction The construction was simply to wind 8 turns of RG174 coax onto a FT140-43 Ferrite Toroid Core. The result of 8 turns achieved an average of 40uH lumped value inductive reactance to common mode RF currents from approximately 10MHz to 70MHz. Parts list. -
FT140-43 Ferrite Toroid Core -
About 0.3mtr of RG174 coax. -
2 x N type chassis mount connector -
Sealed Polycarbonate Enclosures 82 x 80 x 55mm 
Photo 1 Low band choking balun assembled. 
Photo 2 Rear view of the Low band choking balun assembled showing the hose clamp mast attachments. Testing The AIM 4170C antenna analyser recorded in Figure 2 show the Impedance as measured in the coax shield presents an acceptable 2000 Ohms or greater from 14MHz to about 54MHz. 
Figure 3The evaluation of the choking impedance of the balun over a bandwidth from 10MHz- 60MHz. 
Figure 4The evaluation of the balun with a 50 ohm load over a bandwidth from 10MHz- 70MHz. The balun shows a very low SWR from the ideal 1:1 and despite the visual appearance in the graph this result is almost perfect and flat. Also see other baluns and ununs: BALUN 1:1 CHOKE & 1:4 BALUN HF ladder feed-line to coaxial cable combination choke and 1:4 balun. (0.1MHz - 30MHz). BALUN 1:1 CHOKING Choking balun for lower HF and MF bands.(200kHz - 10MHz). CHOKING 1:1 BALUN - HF BANDS Reisert choking balun. (1.0MHz - 30MHz). FT240-43 Ferrite Toroid Core. CHOKING 1:1 BALUN - HF BANDS Reisert choking balun (1.5MHz - 30MHz). FT140-43 Ferrite Toroid Core. CHOKING 1:1 BALUN - LOW VHF BAND Choking balun. (10MHz - 60MHz). FT140-43 Ferrite Toroid Core. BALUN 1:1 CURRENT 1:1 Guanella Current balun using a L15 ferrite core (1.8 - 30MHz). BALUN 1:4 CURRENT 1:4 Guanella Current balun using a L15 ferrite core (1.8 - 30MHz). BALUN 1:4 SINGLE CORE CURRENT 1:4 Guanella Current Balun, single FT240-43 ferrite toroid cores. (0.3MHz - 30MHz). BALUN 1:1 VOLTAGE 1:1 Ruthroff voltage balun using a T-200-2 powdered iron toroid core (1.8 - 30MHz). BALUN 4:1 VOLTAGE 4:1 Ruthroff voltage balun using a T-200-2 powdered iron toroid core (1.8 - 30MHz). BALUN 6:1 VOLTAGE - VERSION 1 6:1 Voltage balun using a L15 ferrite toroid core (1.8 - 30MHz). BALUN 6:1 VOLTAGE - VERSION 2 6:1 Voltage balun using a FT140-43 Ferrite Toroid Core (1.8 - 30MHz) BALUN 9:1 VOLTAGE - VERSION 1 9:1 Voltage balun using a L15 ferrite toroid core (1.8 - 30MHz). BALUN 9:1 VOLTAGE - VERSION 2 9:1 Voltage balun using a FT140-43 Ferrite Toroid Core (0.5 - 60MHz). UNUN 9:1 VOLTAGE 9:1 voltage unun using a T-200-2 powdered iron toroid core (1.8 - 30MHz). UNUN 9:1 VOLTAGE VERSION 2 9:1 voltage unun using a L15 ferrite core (1.8 - 30MHz). UNUN 9:1 VOLTAGE VERSION 3 9:1 voltage unun using a FT140-43 ferrite core (0.5 - 60MHz). TOP OF PAGE Page last revised 25 September, 2019 | 
