• Effective immediately we will be deleting, without notice, any negative threads or posts that deal with the use of encryption and streaming of scanner audio.

    We've noticed a huge increase in rants and negative posts that revolve around agencies going to encryption due to the broadcasting of scanner audio on the internet. It's now worn out and continues to be the same recycled rants. These rants hijack the threads and derail the conversation. They no longer have a place anywhere on this forum other than in the designated threads in the Rants forum in the Tavern.

    If you violate these guidelines your post will be deleted without notice and an infraction will be issued. We are not against discussion of this issue. You just need to do it in the right place. For example:
    https://forums.radioreference.com/rants/224104-official-thread-live-audio-feeds-scanners-wait-encryption.html

Noob Amateur Radio Antenna Question

Status
Not open for further replies.

W6SAE

Member
Premium Subscriber
Joined
Jun 27, 2015
Messages
153
Location
Dixon, California
#1
220 MHz Antenna Question

I recently placed into service a KB9VBR 2-meter J-Pole antenna and am quite pleased with its performance. In addition to 2 meters, it also works well on 70 centimeters. My question is this: would it also be likely to perform well on the 1.25 meter band (220 MHz), since it is between the 2 meter and 70 cm bands?
 
Last edited:

W9BU

Lead Wiki Manager
Super Moderator
Joined
Jul 18, 2004
Messages
5,683
Location
Brownsburg, Indiana
#2
If you multiply 146 MHz, which is in the middle of the 2m band, by 3, you get 438 MHz, which is just below the 440 MHz repeater portion of the 70cm band. In other words, the 440 MHz band is roughly the 3rd harmonic of the 2m band. Consequently, it's not unusual for a 2m antenna to work on 440 MHz.

Whether that same antenna will work on the 222 MHz band is a function of the design of the antenna and what you mean by "work". You really need to check the SWR or use an antenna analyzer to know for certain whether or not the antenna is resonant there.
 

teufler

Member
Premium Subscriber
Joined
Dec 19, 2002
Messages
2,347
Location
ST PETERS, MISSOURI
#3
I doubt it, if you have a swr meter that covers 220, go to low power and check it out. 2 meters would be about 18" at 1/4 wave. 440 is about .5 inches at a quarter wave or about 16 inches at a 3/4 wave antenna, so a 2 meter would sort of work on 440, 224 is about 12" so it is too short for 2 meters and a half wave would be about 24 ', too long for a quarter wave 2 meters
 

jwt873

Member
Premium Subscriber
Joined
Dec 1, 2015
Messages
837
Location
Woodlands, MB
#4
Have you checked the SWR at 440 Mhz?

If you're using a low power handheld, a J pole cut for 145 Mhz will 'work' at 440, but even though it's a multiple, I suspect the SWR would be very high at that frequency. Handhelds have a very good tolerance for SWR so you're probably transmitting and receiving OK despite a high SWR.

The same will probably apply to 220 Mhz...
 
Joined
Mar 12, 2014
Messages
1,056
#5
I'd guess your SWR would be out of whack at 220mhz. When i bought a 220mhz radio, I built a new j-pole antenna from scratch. The dimensions were nowhere near that of the dual band j-pole. You can get 50' of 450ohm ladder line and make cheap j-poles to your heart's content until you get one that works.
 
Joined
Nov 18, 2008
Messages
430
Location
Campbell County, Wyoming
#7
Most antennas will work on or near the 3rd harmonic of their design frequency-not always well but good enough to get by. Most FM and repeater work is 'strong signal' or considerably over the noise -that is one reason squelch circuits can be used. basically, the extra 'losses' of a poor antenna are masked by the extra in other factors. 220 is not harmonically related to two meters so the antenna is not likely to match at all and some type of tuner would be needed.
 

W6SAE

Member
Premium Subscriber
Joined
Jun 27, 2015
Messages
153
Location
Dixon, California
#8
Thanks for all the informative responses. I've been considering buying a 220 MHz transceiver (since my FT-857D doesn't do 220) and trying to decide whether I'd need an additional antenna as well.
 
Status
Not open for further replies.
Top