Old 08-21-2009, 02:34 AM #1
pseudolobster's Avatar
Class 3R Laser
 
Join Date: Jan 2008
Location: BC, Canada
Posts: 1,734
Rep Power: 487
pseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond repute
pseudolobster pseudolobster is offline
Class 3R Laser
pseudolobster's Avatar
 
Join Date: Jan 2008
Location: BC, Canada
Posts: 1,734
Rep Power: 487
pseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond repute
Default Antenna design questions...

I decided to hack apart an old wireless keyboard I had laying around in order to make a small remote control to change the volume on my computer from a distance.

I've hooked everything up okay, and it works fine, though I found out the antenna they used in the original design is a four foot piece of wire wrapped around the entire inside of the keyboard! I'm trying to build a handheld device here, so that just isn't going to work... I've tried cutting the wire down to exactly 1/4 its original length, though the range drops down to about three feet... I tried wrapping that wire around a nail, though the range dropped... I really don't know much about antennas, but I swear there has to be a way I can wrap a few turns of wire around a ferrous core and still get some decent range without having to hold a 4 foot loop of wire above my head.

The transmitter runs at 27mhz... Does anyone have any suggestions how I could cheaply build a small antenna for this thing?


__________________
Custom Text
pseudolobster is offline   Reply With Quote


















Old 08-21-2009, 03:04 AM #2
Hemlock_Mike's Avatar
Class 4 Laser
 
Join Date: Jan 2007
Location: North Iowa
Posts: 6,221
Rep Power: 111795
Hemlock_Mike has a reputation beyond reputeHemlock_Mike has a reputation beyond reputeHemlock_Mike has a reputation beyond reputeHemlock_Mike has a reputation beyond reputeHemlock_Mike has a reputation beyond reputeHemlock_Mike has a reputation beyond reputeHemlock_Mike has a reputation beyond reputeHemlock_Mike has a reputation beyond reputeHemlock_Mike has a reputation beyond reputeHemlock_Mike has a reputation beyond reputeHemlock_Mike has a reputation beyond repute
Hemlock_Mike Hemlock_Mike is online now
Class 4 Laser
Hemlock_Mike's Avatar
 
Join Date: Jan 2007
Location: North Iowa
Posts: 6,221
Rep Power: 111795
Hemlock_Mike has a reputation beyond reputeHemlock_Mike has a reputation beyond reputeHemlock_Mike has a reputation beyond reputeHemlock_Mike has a reputation beyond reputeHemlock_Mike has a reputation beyond reputeHemlock_Mike has a reputation beyond reputeHemlock_Mike has a reputation beyond reputeHemlock_Mike has a reputation beyond reputeHemlock_Mike has a reputation beyond reputeHemlock_Mike has a reputation beyond reputeHemlock_Mike has a reputation beyond repute
Default Re: Antenna design questions...

Loaded antennas are a bitch to figure out without an antenna meter. Perhaps you could find an old CB handheld with a "rubber duck" antenna. It is usually a coil without core about 12" long. 1/4 wavelength at 27 MHz is LOOOONG. Some RC toys running on 27 MHz have short antennas with base loading coils. You nail trick may have been too much inductance and acted as a trap. Try removing the nail.

Mike
__________________
Don't freeze yourself to cold steel
Hemlock_Mike is online now   Reply With Quote
Old 08-21-2009, 04:12 PM #3
Cereal Eater
 
Join Date: Dec 2007
Location: Argentina
Posts: 6,333
Rep Power: 9427
nikokapo has a reputation beyond reputenikokapo has a reputation beyond reputenikokapo has a reputation beyond reputenikokapo has a reputation beyond reputenikokapo has a reputation beyond reputenikokapo has a reputation beyond reputenikokapo has a reputation beyond reputenikokapo has a reputation beyond reputenikokapo has a reputation beyond reputenikokapo has a reputation beyond reputenikokapo has a reputation beyond repute
Send a message via MSN to nikokapo
nikokapo nikokapo is offline
Cereal Eater
 
Join Date: Dec 2007
Location: Argentina
Posts: 6,333
Rep Power: 9427
nikokapo has a reputation beyond reputenikokapo has a reputation beyond reputenikokapo has a reputation beyond reputenikokapo has a reputation beyond reputenikokapo has a reputation beyond reputenikokapo has a reputation beyond reputenikokapo has a reputation beyond reputenikokapo has a reputation beyond reputenikokapo has a reputation beyond reputenikokapo has a reputation beyond reputenikokapo has a reputation beyond repute
Send a message via MSN to nikokapo
Default Re: Antenna design questions...

The thing is that it depends on the amount of "turns" you do around a metallic core and the length of the antenna. As Mike said, try using nothing as the core and let us know how it performs. There's no trick to it, if you need 3 meters you'll have yo use 3 meters of wire. But there are some nice ideas out there like newer car antennas which have a shortened length with more turns (not like the 1 straight wire old car antennas). You should look up for one of those and ask if you can modify it to Rx or Tx at 27MHz.
nikokapo is offline   Reply With Quote
Old 08-21-2009, 06:05 PM #4
pseudolobster's Avatar
Class 3R Laser
 
Join Date: Jan 2008
Location: BC, Canada
Posts: 1,734
Rep Power: 487
pseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond repute
pseudolobster pseudolobster is offline
Class 3R Laser
pseudolobster's Avatar
 
Join Date: Jan 2008
Location: BC, Canada
Posts: 1,734
Rep Power: 487
pseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond repute
Default Re: Antenna design questions...

Thanks for the input guys... I've tried wrapping a full 42" piece of wire around a ballpoint pen tube (I figure that's non-ferrous enough.. I guess this wire is stranded, so it doesn't hold a coil shape on its own), though my range is still only about four feet or so... If I uncoil the wire and hold it out as a big loop I get at least 15-20 feet.

Maybe it's my imagination, but I seem to get better range if I unsolder the other end of the loop, the side that's connected to the gnd side of the circuit... Any input on that?

I think I'm going to check out some thrift stores this weekend and see if I can find an old CB or an RC car or something I can salvage an antenna from... I don't have an oscilloscope or an antenna meter or a frequency generator, or frankly the patience to fiddle with this much further... I just wish this thing ran at 2.4ghz or 900mhz or something, I've got a whole lot of those antennas laying around...
__________________
Custom Text
pseudolobster is offline   Reply With Quote
Old 08-21-2009, 06:29 PM #5
Class 4 Laser
 
Join Date: Nov 2008
Posts: 5,728
Rep Power: 3030
ElektroFreak has a reputation beyond reputeElektroFreak has a reputation beyond reputeElektroFreak has a reputation beyond reputeElektroFreak has a reputation beyond reputeElektroFreak has a reputation beyond reputeElektroFreak has a reputation beyond reputeElektroFreak has a reputation beyond reputeElektroFreak has a reputation beyond reputeElektroFreak has a reputation beyond reputeElektroFreak has a reputation beyond reputeElektroFreak has a reputation beyond repute
ElektroFreak ElektroFreak is offline
Class 4 Laser
 
Join Date: Nov 2008
Posts: 5,728
Rep Power: 3030
ElektroFreak has a reputation beyond reputeElektroFreak has a reputation beyond reputeElektroFreak has a reputation beyond reputeElektroFreak has a reputation beyond reputeElektroFreak has a reputation beyond reputeElektroFreak has a reputation beyond reputeElektroFreak has a reputation beyond reputeElektroFreak has a reputation beyond reputeElektroFreak has a reputation beyond reputeElektroFreak has a reputation beyond reputeElektroFreak has a reputation beyond repute
Default Re: Antenna design questions...

1/4 wave at 27mHz is roughly 102". If you take a 102" piece of wire and coil it up you would have a loaded 1/4 wave vertical antenna. Two 102" lengths, one on each side of the transmission line is a 1/2 wave dipole. I believe you can load loops as well, but I can't remember if it complicated things or not. Fir a more manageable amount or wire, you could use 1/8 wave at 51". The length of wire is crucial to having good propagation, since any length other than exactly 1/8, 1/4, 1/2, 5/8, and full wave will have a standing wave ratio (SWR) that is too poor, which in turn causes some of the output power to be reflected back along the transmission line into the final amplifier. In high powered systems, a poor SWR can damage the transmitter. In low powered systems like yours, it just blocks a great deal of the power from leaving the antenna.
__________________
Laser Resources (for n00bs and veterans alike!)

Sam's Laser FAQ (The Laser Bible)

http://www.repairfaq.org/sam/laserfaq.htm

RP Photonics Encyclopedia of Laser Physics and Technology

http://www.rp-photonics.com/encyclopedia.html

ULTIMATE DIY PROJECTOR REFERENCE

http://nqlasers.com/scannerreference...itle=Main_Page

SUCCESS is the best revenge.

Last edited by ElektroFreak; 08-21-2009 at 06:33 PM.
ElektroFreak is offline   Reply With Quote
Old 08-21-2009, 06:38 PM #6
lasersbee's Avatar
Class 4 Laser
 
Join Date: Sep 2008
Location: Quebec, Canada
Posts: 16,845
Rep Power: 1028649
lasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond repute
lasersbee lasersbee is offline
Class 4 Laser
lasersbee's Avatar
 
Join Date: Sep 2008
Location: Quebec, Canada
Posts: 16,845
Rep Power: 1028649
lasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond repute
Default Re: Antenna design questions...

Some of my old R/C radios have a 27Mhz receiver with an antenna
that is about 35-45" long... and if we don't use the full length...
the max range drops...

Jerry
__________________

J.BAUER Electronics Home Page

LaserBee Laser Power Meter Products meet your needs
at affordable Prices:
See them all here on LPF

LaserBee Power Meter products ALWAYS in Stock
and ready to ship

Also available on eBay:Check availability here..

Subsidary: Pharma Electronic Solutions


This banner is available to and can be copied/used FREE by any LaserBee owner
lasersbee is offline   Reply With Quote
Old 08-21-2009, 11:03 PM #7
pseudolobster's Avatar
Class 3R Laser
 
Join Date: Jan 2008
Location: BC, Canada
Posts: 1,734
Rep Power: 487
pseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond repute
pseudolobster pseudolobster is offline
Class 3R Laser
pseudolobster's Avatar
 
Join Date: Jan 2008
Location: BC, Canada
Posts: 1,734
Rep Power: 487
pseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond repute
Default Re: Antenna design questions...

So, I measured the stock antenna in this thing and it's 49.5 inches long... Not sure what to make of that... I think I may try the 52 inches Electrofreak suggested..

I've been getting a huge drop in range if I coil it... The only way I can get full range out of it is to hold the loop up in the air, without it crossing over itself at any point... It also works well if I unsolder the other end of the loop and hold it straight out... Unfortunately I'm beginning to get the impression I'll need a four foot long stick attached to this thing if I want to use it from more than three feet away, in which case I'd be better off using the four foot stick itself to change the volume.
__________________
Custom Text
pseudolobster is offline   Reply With Quote
Old 08-24-2009, 11:09 PM #8
pseudolobster's Avatar
Class 3R Laser
 
Join Date: Jan 2008
Location: BC, Canada
Posts: 1,734
Rep Power: 487
pseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond repute
pseudolobster pseudolobster is offline
Class 3R Laser
pseudolobster's Avatar
 
Join Date: Jan 2008
Location: BC, Canada
Posts: 1,734
Rep Power: 487
pseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond repute
Default Re: Antenna design questions...

Well, I finished up my remote today... I replaced the big ugly pushbuttons with one of those "ninja remotes" from DX, and wired it up to the stop, play, fast fwd, rew, volume up and down and mute. I also replaced the AA batteries with a CR2032 button cell because honestly, they're cheaper than AA's and I have a million of them. I included pretty pictures if anyone's interested...

Anyways, I still haven't found an old RC car or CB radio, so the hunt is still on for an antenna shorter than this 49.5" piece of wire...
Attached Thumbnails
Antenna design questions...-dsc01802.jpg  
__________________
Custom Text
pseudolobster is offline   Reply With Quote
Old 08-24-2009, 11:20 PM #9
lasersbee's Avatar
Class 4 Laser
 
Join Date: Sep 2008
Location: Quebec, Canada
Posts: 16,845
Rep Power: 1028649
lasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond repute
lasersbee lasersbee is offline
Class 4 Laser
lasersbee's Avatar
 
Join Date: Sep 2008
Location: Quebec, Canada
Posts: 16,845
Rep Power: 1028649
lasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond repute
Default Re: Antenna design questions...

Have you looked at xmit/rcv units like these...

Mini RF Wireless Radio Transmitting Module TM50-1 on eBay.ca (item 300339515235 end time 24-Aug-09 20:00:00 EDT)

RF Wireless Radio Receiver Module w/ Super Power Saving on eBay.ca (item 290340743554 end time 25-Aug-09 15:00:00 EDT)

Or even a partial ready unit like this one....

http://cgi.ebay.ca/4CH-Superregenera...lenotsupported


I've used similar pre-fabricated PCBs in the past... They worked for me...
And they are not expensive... IMO

Jerry
__________________

J.BAUER Electronics Home Page

LaserBee Laser Power Meter Products meet your needs
at affordable Prices:
See them all here on LPF

LaserBee Power Meter products ALWAYS in Stock
and ready to ship

Also available on eBay:Check availability here..

Subsidary: Pharma Electronic Solutions


This banner is available to and can be copied/used FREE by any LaserBee owner
lasersbee is offline   Reply With Quote
Old 08-24-2009, 11:53 PM #10
pseudolobster's Avatar
Class 3R Laser
 
Join Date: Jan 2008
Location: BC, Canada
Posts: 1,734
Rep Power: 487
pseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond repute
pseudolobster pseudolobster is offline
Class 3R Laser
pseudolobster's Avatar
 
Join Date: Jan 2008
Location: BC, Canada
Posts: 1,734
Rep Power: 487
pseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond reputepseudolobster has a reputation beyond repute
Default Re: Antenna design questions...

Thanks Jerry, I'll keep those in mind for future projects... For this one though, a wireless keyboard was a better solution IMO, no need for drivers or anything, windows just detects it as a generic multimedia keyboard, it works in all programs, it even works in linux, no extra messing around... For something that I'm not hooking up to a computer though, those tx/rx pairs look great, and the price is really decent. I'll definitely bookmark those.
__________________
Custom Text
pseudolobster is offline   Reply With Quote
Old 08-25-2009, 12:51 AM #11
lasersbee's Avatar
Class 4 Laser
 
Join Date: Sep 2008
Location: Quebec, Canada
Posts: 16,845
Rep Power: 1028649
lasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond repute
lasersbee lasersbee is offline
Class 4 Laser
lasersbee's Avatar
 
Join Date: Sep 2008
Location: Quebec, Canada
Posts: 16,845
Rep Power: 1028649
lasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond repute
Default Re: Antenna design questions...

I was looking around and found this Thread... Maybe got some Ideas there...

PCB antenna at 27MHz

Jerry
__________________

J.BAUER Electronics Home Page

LaserBee Laser Power Meter Products meet your needs
at affordable Prices:
See them all here on LPF

LaserBee Power Meter products ALWAYS in Stock
and ready to ship

Also available on eBay:Check availability here..

Subsidary: Pharma Electronic Solutions


This banner is available to and can be copied/used FREE by any LaserBee owner
lasersbee is offline   Reply With Quote
Reply





Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

























Privacy Policy | Advertising Disclaimer | Terms of Use


 


All times are GMT. The time now is 02:11 AM.


Powered by: vBulletin
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO
Privacy Policy | Advertising Disclaimer | Terms of Use
Copyright (C) 2017 Laser Pointer Forums, LLC