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I see... thanks for the reply.
I was confused by the toroid in transmission. When transmitting, the ferrite toroid is usually near the transceiver, but for other reason: to avoid the RF catch by the coax shield or reflected due to a mismatched antenna to reach the transceiver (it can cause RF shock to people and interferences). In reception, yes, you're right, but I think that only if the coax shield is correctly grounded. The signal at the received is not the one coming through the line, but the difference between the signal coming through the line and the signal coming though the shield, so grounding the shield puts the shield signal to zero, and then only the line signal is considered. If the radio is operated from batteries or ungrounded, both signals will count and the noise will be noticed, whether it comes through the line or through the coax. Maybe I'm wrong. RF is a very empirical "science" and experiencie is more valuable than books ![]() ![]() I spent great moments with a long wire (30 meters or 100 feet) coupled with a MFJ antenna tunner with long wire coupler (MFJ-941E) in the country. Now I have a constant electrical noise in the city in all the band, about S7-S9, 24h... I'm limited to strong signals. Best regards. Kees wrote: Hi Well, the coax receives it on the outer side. It would travel up to the balun and goes from there into the coax inside back to the receiver. That's why I put it up there. Kees On Mon, 21 Jun 2004 12:53:59 +0200, Nacho wrote: Hello. Just a question. Why is the ferrite toroid near the antenna instead of near the receiver? It is used to supress the waves received by the coax, but at the far side from the transceiver, the supress will be minimum... Best regards. Kees wrote: Hello fellow shortwave listeners ! More info to make a T2FD yourself, like I did mine, please have a look at: http://members.home.nl/rita.kees/t2fdmake.html I hope you can appreciate it and use it for your practice. I will be glad to answer your questions. 73/cheers Kees |
#2
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NACHO,
IMHO: Your T2FD could also use a "Feed-Line-Isolator" at the 'junction' of the Receiver and Coax Cable. Take a look at the Wellbrook "Low Noise Antenna" 'design concept' using two components they manufactu the Universal Magnetic Balun (UMB) and the Antenna Feed Isolator (Feed-Line-Isolator). GoTo= http://www.wellbrook.uk.com/longwire.html FWIW: This webpage has two Drawings/Diagrams "The Wrong Way" and "The Correct Way" plus a brief description of the 'Whys' and 'Hows' of this "Low Noise Antenna" design concept. NOTE: These are labled as "Longwire" Antenna Baluns, but in reality they are mostly used on the more common "Random Wire" Antennas that the majority of SWL are able to build and use in their backyards or outside/inside the house. iane ~ RHF .. .. = = = Nacho wrote in message = = = ... I see... thanks for the reply. I was confused by the toroid in transmission. When transmitting, the ferrite toroid is usually near the transceiver, but for other reason: to avoid the RF catch by the coax shield or reflected due to a mismatched antenna to reach the transceiver (it can cause RF shock to people and interferences). In reception, yes, you're right, but I think that only if the coax shield is correctly grounded. The signal at the received is not the one coming through the line, but the difference between the signal coming through the line and the signal coming though the shield, so grounding the shield puts the shield signal to zero, and then only the line signal is considered. If the radio is operated from batteries or ungrounded, both signals will count and the noise will be noticed, whether it comes through the line or through the coax. Maybe I'm wrong. RF is a very empirical "science" and experiencie is more valuable than books ![]() ![]() I spent great moments with a long wire (30 meters or 100 feet) coupled with a MFJ antenna tunner with long wire coupler (MFJ-941E) in the country. Now I have a constant electrical noise in the city in all the band, about S7-S9, 24h... I'm limited to strong signals. Best regards. .. |
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