Eznec is your friend Dave. Having used a previously short Vertical 51ft for 20+ years, the top loading is not your problem. Because the feed Z is low you will require longer radials. Mine are typically 0.4 wavelengths. I will stand corrected but the formula is E (efficiency) = Feed Z/ Feed Z plus loss (the loss being mainly ground loss) So typically with a short vertical we could have 12/ 12+ plus loss which could be any amount dependent on your radial system. The only way to deal with this is either by a vast radial system or a taller vertical. In the end it's all a numbers game. 73 Clive GM3POI (306 current confirmed)
-----Original Message----- From: Topband [mailto:[email protected]] On Behalf Of David Cole via Topband Sent: 13 June 2017 21:08 To: [email protected] Subject: Topband: Short Verticals Hi all - Assuming a standard 1/4 wave vertical is 36 ohms - is there any formula that will calculate the Z if the vertical is short and brought to resonance by top loading wires - I understand the Z will be less - but how much by ? I am trying to use the formula on ON4UN disc to calculate the approx LC ratios for a Lahlum-Lewallen phasing system. Thanks Dave g3rcq _________________ Topband Reflector Archives - http://www.contesting.com/_topband _________________ Topband Reflector Archives - http://www.contesting.com/_topband
