Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

donate to eham
   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Base antenna versus Mobile antenna  (Read 1414 times)
THENUTS15

Posts: 3




Ignore
« on: November 24, 2017, 12:49:41 AM »

Hi,

1)was wondering the differences btw those 2 other than its portability.

2)I am planning to setup a VHF base station but my problem is the antenna will be on 2nd floor(Concrete house).I have no access to earth my antenna mast to ground floor.Any suggestion?

Thank you.
Logged
ONAIR
Member

Posts: 3535




Ignore
« Reply #1 on: November 24, 2017, 02:35:48 AM »

Hi,

1)was wondering the differences btw those 2 other than its portability.

2)I am planning to setup a VHF base station but my problem is the antenna will be on 2nd floor(Concrete house).I have no access to earth my antenna mast to ground floor.Any suggestion?

Thank you.
   Just build a ground plane, or a small beam!  Wink
Logged
KF4ZGZ
Member

Posts: 40


WWW

Ignore
« Reply #2 on: November 24, 2017, 02:48:17 AM »

Google "homebrew SO-230 ground plane antenna".
A SO-239 connector and some wire and off you go!
I Have made them out of random wire coathangers with great results.


Matt
Logged
K5LXP
Member

Posts: 5329


WWW

Ignore
« Reply #3 on: November 24, 2017, 04:09:33 AM »

The ground floor/earth wouldn't be ground for any antenna anyway.  Use a groundplane of resonant radials per ZGZ or use a balanced antenna that doesn't require a groundplane (beam, dipole, loop, etc).

A "base" antenna made up of a mobile mag mount on a cookie sheet or pizza pan is about as simple and convenient as you can get.


Mark K5LXP
Albuquerque, NM
« Last Edit: November 24, 2017, 04:11:38 AM by K5LXP » Logged
KD7RDZI2
Member

Posts: 229




Ignore
« Reply #4 on: November 24, 2017, 07:04:12 AM »

I would go for a vertical dipole in case you what vertical polarization. I made one with a BNC-banana adapter for Vhf and Uhf and enameled copper wire (cutting the dipoles at 95% of the theoretical length the antenna resonates perfectly). It's like a fan dipole so the V and U dipoles are just parallel. I found essentially no interaction as for SWR. I used copper as it is one of the best RF conductor especially at high frequencies. I can tell you there is quite a difference compared to the stock whip of HT. The cost is almost zero and the dipole always works with certainty.
« Last Edit: November 24, 2017, 07:10:29 AM by KD7RDZI2 » Logged
KB1GMX
Member

Posts: 1505




Ignore
« Reply #5 on: November 24, 2017, 09:58:48 AM »

Ground at VHF is for lightning protection and provides no significant
radiation for the signal.

With that disposed of a mobile whip in a cookie sheet is a good start.
ground plane antennas J poles and other are also candidates.

Depending on distance the type coax you use may be important.  For
short runs under 25ft RG58 is adequate, for longer Rg8X and and 75-100ft
or more consider LMR400. 

One note:  Height is important the higher the better,

All of the above assumes local coverage operation (repeaters and simplex).

Keep it simple, and high and have fun.

Allison
Logged
N1LO
Member

Posts: 1108


WWW

Ignore
« Reply #6 on: November 25, 2017, 07:07:45 AM »

I think you are referring to needing a ground plane to function properly. A base antenna usually has three ground radials and does not need any other connection to metal for a ground plane to work properly.

However a mobile antenna usually has to go on a mount with sheet metal around it in order to work properly. It is possible to take a mobile antenna and attach a ground radial kit. I have built one of these and it works well. Not sure if these are available ready made on the market to buy right now. Would be a good money maker for someone if this idea catches on (hint hint entrepreneurs, we know you're sandbagging!).
Logged
WA3SKN
Member

Posts: 6517




Ignore
« Reply #7 on: November 25, 2017, 11:20:50 AM »

You only ground the mast for static dissipation.  And every AC outlet in the area can supply that.  Since you are on the 2nd floor, why bother?
Once you get the antenna above 60 feet or so, it does make a difference.
73s.

-Mike.
Logged
THENUTS15

Posts: 3




Ignore
« Reply #8 on: November 26, 2017, 03:05:31 AM »

Thanks for the input guys  Wink

I am planning to get Diamond BC100 antenna and  Yaetsu FT2900.Anybody have feedback on this combinations?
I cant seems to get the review for Diamond BC100.
Logged
KD7RDZI2
Member

Posts: 229




Ignore
« Reply #9 on: November 27, 2017, 01:27:50 AM »

The BC-100 seems quite a peculiar antenna! It covers all the VHF starting from 115. Has a bit less gain and similar to a ground plane antenna. BTW the antenna is shunted and you should see a  DC short circuit with a meter, so you should have no problems with statics.
Logged
NEVBEN
Member

Posts: 96




Ignore
« Reply #10 on: December 02, 2017, 09:48:51 PM »

Thanks for the input guys  Wink

I am planning to get Diamond BC100 antenna and  Yaetsu FT2900.Anybody have feedback on this combinations?
I cant seems to get the review for Diamond BC100.

The BC100 should work fine.  I just installed a similar Diamond base antenna and I was impressed with the quality of the build, and pleased with the result.  In my experience with 2 meters, the height above average terrain is more important than a high-gain antenna.  It's not even so important to get it ultra-high -- just higher than things that will block the signal.  If it's down in a hole or up against a wall, there's no practical amount of gain or amplifier power that is going to work better than getting it up in the clear.

I have a Yaesu FT2900R for 7 years now.  I also just bought a couple Kenwood TH-281A.  These are basic 2m-only transceivers.  I bought the Kenwoods because I think I prefer the user interface.  Don't choose the FT2900R just for the 75W power.  That's only 0.6db gain over a 65W transmitter and it doesn't make the receiver any better.  You can get more gain with an antenna, but more gain isn't really what you need for 2 meters.

I've never used an ICOM IC-2300H, but it's the other popular 144MHz mono-band mobile radio to consider.

Both the Kenwood and the Yaesu have poor audio amps.  Notice they rate them at 10% THD -- that's awful distortion.  For a base, don't turn the volume past 1/4 (or you'll get clipping and distortion), and use an amplified external speaker.  FM audio can be lush, if you're not cranking an amp to 10% THD, clipping and sending it to a tiny built-in speaker.

I use my 2 meter radios to communicate with one other ham in particular.  But if I wanted to talk to more hams, or even as many as possible, most of the advice I've read is to get a dual-bander.  You might also consider whether you want to be on a digital mode in your area.  Personally, I don't.  I pretty much use one frequency and one call sign.  But what you want to do and whether a single band radio like the FT2900R is best or not is something to consider.

My 2 meter radio meets a need for communication, but for experimentation and a fun hobby, there is a lot more to do with HF.  I would much rather do something with HF than spend more for UHF on a dual-band mobile.

An HF base that includes the 2 meter band is probably the best in performance and features, but it would have cost and complexity an order of magnitude above a monoband mobile unit.
Logged
NEVBEN
Member

Posts: 96




Ignore
« Reply #11 on: December 02, 2017, 10:19:14 PM »

The BC-100 seems quite a peculiar antenna!

It's a 5/8 wave vertical inside a fiberglass reinforced plastic tube with three radials.   An antenna like this will have wide receive coverage, but they are cut to length by the installer to tune them for transmitting.  Typically, they ship close to the length needed for the Amateur 2m band (~144MHz), and commercial or public safety users cut them for a better match for ~155MHz, 160MHz or whatever they're using.  If you're going to use it at 147MHz, you might be able to trim it slightly for a better match.  Using an antenna analyzer will get you a more exact result than a cutting chart.

For 2 meter verticals, typical patterns for commercially produced antennae are 1/4 wave, 1/2 wave, and 5/8 wave.  Those are all under ~48" and so popular for mobiles.  The typical home-brew 2 meter "ground-plane" antenna is a 1/4 wave vertical with four radials.  A base could use any one of those or a longer antenna typically with two 7/8 wave elements stacked and phased (about 10.5'), or three 5/8 wave elements stacked and phased (about 15').  One could continue to stack more elements but commercial products don't typically go beyond that because it becomes impractical and the HAAT gives a more meaningful result than stacking more than three elements.  There are of course also beams which can work very well if the goal is uplink/downlink to a specific high-level repeater or to connect two specific sites.  Also, I understand horizontally polarized dipoles (etc.) can be meaningful for working AM or SSB on 2 meters, but most FM stations and repeaters have a vertically polarized antenna.

Logged
WA3SKN
Member

Posts: 6517




Ignore
« Reply #12 on: December 06, 2017, 06:05:28 AM »

I would first check what repeaters are in your area.
However, for 2 meters, the bc100 should work just fine.
The FT2900 should work just fine.
I would recommend getting a 25-30 amp power supply.  You can use it later with acquired HF eqpt.
The FT2900 has a "close-talking" microphone, so hold it near your mouth when talking.
73s.

-Mike.
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!