| Welcome to the official Charlie Tango DX Group CB And Amateur Radio Forum. You are visiting the UK's biggest and most active CB Radio club.. We hope you enjoy your visit. Charlie Tango DX is a group dedicated to Hobby Radio Users in all forms, whether CB, Amateur, PMR446, Scanning and Short Wave Listening. We are a very active and friendly group that welcomes anyone from anywhere in the world who has an interest in Radio, regardless of their level of experience, their equipment, their location, or their radio preference. We have members varying from fully qualified operators on the Amateur Bands, to newcomers who have just bought a PMR446 set, and many CBers both old and new. All are equal on the Site. The CT Site contains many reviews, tips and modifications within the forums, and we take pride that no sensible question is ever left unanswered, and nobody is ever belittled or mocked for asking an honest question, no matter how simple it may seem. We were all new to the hobby once. You're currently viewing our forum as a guest. This means you are limited to certain areas of the board and there are some features you can't use. If you join Charlie Tango you'll be able to access member-only sections, and use member-only features such as customizing your profile, sending personal messages, voting in polls, viewing modifications and more. If you are not yet a member: Registration is simple, fast, and completely free. Simply CLICK HERE to start the Registration process. Your application will need to include your personal name and approximate location, it will require you to confirm your email, and then be signed-off by one of our Admin Staff, but this is usually completed within 24 hours (48 max) |
| Thick question time !; Horizontal vs vertical dipole impedance | |
|---|---|
| Tweet Topic Started: Sunday, 30. August 2015, 18:36 (302 Views) | |
| Gazby | Sunday, 30. August 2015, 18:36 Post #1 |
26 Charlie Tango 1766
![]()
|
Why does a horizontal or inverted V work with 50 ohm coax but a vertical is recommended at 70 ohm ? Also, why is there no mention of this on a chope bought horizontal dipole ? ... |
![]() |
|
| Staffy 48 | Sunday, 30. August 2015, 19:01 Post #2 |
![]()
|
The impedance of half wave dipoles are 70 ohms, if you use a 50 ohm feed, (coax), and we all do the SWR reading will never be below 1.5:1, true reading that is. |
![]() |
|
| Gazby | Sunday, 30. August 2015, 19:16 Post #3 |
26 Charlie Tango 1766
![]()
|
Cheesrs Staffy, the inverted V in my garage uses 50 ohm cable and swr is minimal, like 1.2 ish. Angle of V is probably about 130 degrees |
![]() |
|
| Staffy 48 | Sunday, 30. August 2015, 19:40 Post #4 |
![]()
|
The true impedance of a half wave Dipole if I remember is actually 72 ohms, you can get 70 ohm coax but we all use 50 ohm, and the difference between 50 and 70 ohm feed for an antenna is negligible, I started reading up on different types of antenna a few months ago and I'm afraid I was trying to run before I could walk. Due to taking the foundation course I knocked the antennas on the head for a bit, and now, in the very near future I'll be doing the intermediate course so once again antennas will be on the back burner. I rather fancy making a 2 element cubical quad for 10/11 metres, a simple but very efficient beam and inexpensive to build. |
![]() |
|
| The DB | Monday, 31. August 2015, 04:02 Post #5 |
![]()
|
The difference in impedance in the "real world" comes from the antenna's orientation in relation to the earth below, and its height above said earth. If your dipole is less than one wavelength high the earth has the effect of lowering the feedpoint impedance. The lower the antenna is the bigger the change is. Actually, this is often the case with multiple antenna designs, including virtually every commercial antenna on the market. To complicate matters more, different earth qualities will affect the feedpoint of antennas differently. Another aspect of the inverted V is the angle in the antenna design. If the two sides are straight on from each other, you will have the highest impedance. However, once you lower the tips of the antenna, creating an angle, that will lower the feedpoint impedance as well. Another antenna with a similar, yet opposite, effect is the quarter wavelength vertical antenna with horizontal radials. When the radials are 90 degrees from the vertical element the antenna has near 35 ohms (give or take) feedpoint impedance. As you angle the radials down, in essence making the antenna "straighter" that impedance begins to rise, and will eventually rise to the near 70-75 ohms that a vertical center fed dipole tends to have. If you want that so called "perfect" SWR match with such an antenna, an angle of 45 degrees will get you very close, not that it will make a difference when it comes to performance. That 45 degree angle is a bit much for an inverted V, I would think 20 to 30 degrees would work better for it. If you look at similar antennas in different installations, you will find that they have yet other feedpoint impedances. Everything in the area of the antenna, as well as what people see as minor changes in the antenna's design, all have an effect on said feedpoint impedance. It is the nature of antennas. It can get complicated, but really, its not worth worrying about, as long as you have a reasonably low SWR these antenna designs should work fine. The DB |
![]() |
|
| Gazby | Monday, 31. August 2015, 09:34 Post #6 |
26 Charlie Tango 1766
![]()
|
Cheers chaps ! If in doubt - get ya swr Meter out |
![]() |
|
| 1 user reading this topic (1 Guest and 0 Anonymous) | |
| « Previous Topic · Aerials, RF & QRM Section · Next Topic » |
| Track Topic · E-mail Topic |
8:49 AM Jul 11
|
All Rights Reserved - No Part Of This Site May Be Copied Without Prior Written Permission. CharlieTango.co.uk have a legal Common Law Trademark and Registered Copyright #S0RN-LTC9-8CXT-LZLU of the brand "Charlie Tango" since 2009 and related Copyrights in place for domain names, Logos, images, format and layout of this website and associated material. charlietango.co.uk & charlietango.uk
View My Stats
DOMAIN NAMES FOR SALE
ConspiracyEffect.com | V5Bid.com Auction | 041183.com | Hiya.Mobi | VR Portal.Net | TrainerSox.com | CoinStealth.com | ChoccyBox.com Domains | FlutterBets.com | CharlieTango.UK | HallmarkedGold.com | MozSubmit.com | HorizontalEarth.com
CharlieTango.co.uk contact email leewardill@gmail.com






8:49 AM Jul 11