Twin Lead Folded Dipole Antenna and example demo eTCL calculator
Twin Lead Folded Dipole Antenna and example demo eTCL calculator, numerical analysis
This page is under development. Comments are welcome, but please load any comments in the comments section at the bottom of the page. Please include your wiki MONIKER in your comment with the same courtesy that I will give you. Its very hard to reply intelligibly without some background of the correspondent. Thanks,gold
- Twin Lead Folded Dipole Antenna and example demo eTCL calculator, numerical analysis
- Introduction
- Alternate Text
- Appendix Code
- Draft Figures
- Draft Figures
- figure. TWIN LEAD FOLDED DIPOLE ANTENNA: KEY DIMENSIONS
- figure. TWIN LEAD FOLDED DIPOLE ANTENNA: GEOMETRY AND FEED
- figure. eTCL TWIN LEAD FOLDED DIPOLE CALCULATOR DEMO
- figure. TWIN LEAD FOLDED DIPOLE ANTENNA: KEY DIMENSIONS
- figure. TWIN LEAD FOLDED DIPOLE: GEOMETRY AND CONSTRUCTION
- figure. eTCL TWIN LEAD FOLDED DIPOLE CALCULATOR DEMO
- figure. WAVELENGTH CALCULATION TABLE
- figure. TWIN LEAD FOLDED DIPOLE vs SIMPLE DIPOLE
- figure. PRACTICAL CONSTRUCTION STEPS
- figure. RADIATION PATTERN AND MOUNTING
- figure. DESIGN RULES OF THUMB
- figure. EXAMPLE CALCULATOR TESTCASES
- figure. FOLDED DIPOLE VARIANTS
- figure. SALVAGE AND MOUNTING OPTIONS
- figure. COMPARISON TABLE: ANTENNA TYPES
- Comments Section
Introduction
gold Here is some eTCL starter code for a twin lead folded dipole antenna. The impetus for these calculations was checking calculations for a dipole antenna. Most of the testcases involve assumptions and rules of thumb.
The procedure starts with finding the radio wavelength in meters, wavelength = (velocity_factor*speed_of_light)/(megahertz* 1E6). The antenna length is set for half wavelength and is multipled by a correction factor for end distortion. The antenna height above ground is 2 wavelengths above ground.
# following statements can be pasted into eTCL console
set project 1.0 set wavelength [/ [* .95 300E6] [* 98.E6] ] # 2.908 meters set wavelength [/ [* .95 300E6] [* 57.E6] ] # 5.0 meters set wavelength [/ [* .95 300E6] [* 100.E6]] # 2.85 meters
Alternate Text
Gist. A computer program in Tool Control Language TCL was used to design a half wave dipole antenna for 100 Mhz on FM. The half wave dipole is excellent for classical music on city FM, but can be used (somewhat) for broadcast AM. Either twin lead or double appliance wire is used to increase effective conductor width or Antenna Bandwidth for FM reception. The wire antenna from scrap appliance cord is tacked to a varnished "pretty" wood board for cosmetics, if not in a college dorm or attic.
The antenna length is set for half wavelength and is multiplied by a correction factor for end distortion. The minimum antenna height above ground is 2 wavelengths above ground, but the used electrical cord can be tacked to roof rafters. The half wave dipole receives 100 MHZ FM with a gain of ~~2 dBi. Checking calculations for a folded dipole antenna, sometimes called a "T" antenna.
The procedure starts with finding the radio wavelength in meters, wavelength equals (velocity_factorspeed_of_light)/(megahertz 1E6). The antenna length is set for half wavelength and is multiplied by a correction factor for end distortion. The minimum antenna height above ground is 2 wavelengths above ground.
Crafting notes. The twin lead version of the "T" can be tacked at full length to a wall, ceiling, or attic rafter. In an alternate version, the halfwave antenna from surplus appliance cord antenna is tacked to a varnished "pretty" wood board for cosmetics, if not in a college dorm or attic. The surplus appliance cord on antenna was selected for economy, but the old fashioned wire was extra sturdy and easy to work with. In contrast to the appliance cord, the traditional twin lead wire was very difficult to stay put on the board. I am adding a generous fudge length of 2 inches to the initial wire cut for soldiering leads and tap placement. On the scrap boards of uncertain size, the antennas have end curls, and appear somewhat like the horn-shape of Texas long horn cattle. The smaller half wave dipole antennas receive 100 MHZ FM and (somewhat) Broadcast AM too, with an antenna gain of ~~2 dBi. Continuing as an experiment, the smaller half wave dipole antennas can be backed with a metal or foil sheet as reflector for higher antenna gain, ~~ 4 dBi . As a concept or thought experiment, it would seem possible that the constructed wire antenna could be tacked to a room corner or on a ceiling as a "V" antenna for higher antenna gain, ~~2X.
Testcases Section
In planning any software, it is advisable to gather a number of testcases to check the results of the program. The math for the testcases can be checked by pasting statements in the TCL console. Aside from the TCL calculator display, when one presses the report button on the calculator, one will have console show access to the capacity functions (subroutines).
Testcase 1
| table 1 | printed in | tcl wiki format |
|---|---|---|
| quantity | value | comment, if any |
| testcase number: | 1 | |
| 98.1 : | center frequency megahertz | |
| 1.0 : | optional | |
| 1.0 : | optional | |
| 2.90519877675841 : | wavelength meters | |
| 1.452599388379205 : | half wavelength meters | |
| 1.467125382262997 : | corrected .5L antenna length meters or 57.18895412844037 inches | |
| .5 : | antenna lead meters | |
| 5.81039755351682 : | height above ground meters |
Testcase 2
| testcase number: | 2 | |
| 100.1 : | center frequency megahertz | |
| 1.0 : | optional | |
| 1.0 : | optional | |
| 2.8471528471528473 : | wavelength meters | |
| 1.4235764235764237 : | half wavelength meters | |
| 1.437812187812188 : | corrected .5L antenna length meters or 56.046317682317685 inches | |
| .5 : | antenna lead meters | |
| 5.694305694305695 : | height above ground meters |
Testcase 3
| table 3 | printed in | tcl wiki format |
|---|---|---|
| quantity | value | comment, if any |
| testcase number: | 3 | |
| 57.1 : | center frequency megahertz | |
| 1.0 : | optional | |
| 1.0 : | optional | |
| 4.991243432574431 : | wavelength meters | |
| 2.4956217162872156 : | half wavelength meters | |
| 2.5205779334500877 : | corrected .5L antenna length meters or 98.25282661996499 inches | |
| .5 : | antenna lead meters | |
| 9.982486865148863 : | height above ground meters |
Screenshots Section
figure 1.
figure 2.
figure 3.
figure 4.
figure 5.
figure 6.
figure 7. Alternate Salvage Antenna stripped
figure 8. Alternate Salvage Antenna tinned
figure 9. Alternate Salvage Antenna Mounted on Scrap Board
References:
- goggle "twin lead dipole"
- Wikipedia on dipole
- Antennas, see snowflake antenna, tikalon blog,
- May 16, 2016, Dev Gualtieri, excellent article
Appendix Code
appendix TCL programs and scripts
# pretty print from autoindent and ased editor
# Twin Lead Dipole Antenna calculator
# written on Windows XP on eTCL
# working under TCL version 8.5.6 and eTCL 1.0.1
# gold on TCL WIKI, 15dec2016
package require Tk
namespace path {::tcl::mathop ::tcl::mathfunc}
frame .frame -relief flat -bg aquamarine4
pack .frame -side top -fill y -anchor center
set names {{} {center frequency megahertz :} }
lappend names {optional, :}
lappend names {optional, :}
lappend names {answers: whole wavelength meters :}
lappend names {half wavelength meters :}
lappend names {corrected .5L antenna length meters: }
lappend names {lead meters: }
lappend names {height above ground meters:}
foreach i {1 2 3 4 5 6 7 8} {
label .frame.label$i -text [lindex $names $i] -anchor e
entry .frame.entry$i -width 35 -textvariable side$i
grid .frame.label$i .frame.entry$i -sticky ew -pady 2 -padx 1 }
proc about {} {
set msg "Calculator for Twin Lead Folded Dipole Antenna
from TCL WIKI,
written on eTCL "
tk_messageBox -title "About" -message $msg }
proc pi {} {expr acos(-1)}
proc calculate { } {
global answer2
global side1 side2 side3 side4 side5
global side6 side7 side8
global testcase_number
incr testcase_number
set side1 [* $side1 1. ]
set side2 [* $side2 1. ]
set side3 [* $side3 1. ]
set side4 [* $side4 1. ]
set side5 [* $side5 1. ]
set side6 [* $side6 1. ]
set side7 [* $side7 1. ]
set side8 [* $side8 1. ]
set megahertz $side1
set conv_factor $side5
set speedoflight 300E6
#set velocityfactor .87 ; alternate velocity factor
set velocityfactor .95
set wavelength [/ [* $velocityfactor $speedoflight] [* $megahertz 1E6 ] ]
set halfwavelength [* $wavelength .5 ]
set antennacorrection [* $halfwavelength 1.01 ]
set antennalead .5
set heightaboveground [* 2. $wavelength ]
set side4 $wavelength
set side5 $halfwavelength
set side6 $antennacorrection
set side7 $antennalead
set side8 $heightaboveground
}
proc fillup {aa bb cc dd ee ff gg hh} {
.frame.entry1 insert 0 "$aa"
.frame.entry2 insert 0 "$bb"
.frame.entry3 insert 0 "$cc"
.frame.entry4 insert 0 "$dd"
.frame.entry5 insert 0 "$ee"
.frame.entry6 insert 0 "$ff"
.frame.entry7 insert 0 "$gg"
.frame.entry8 insert 0 "$hh"
}
proc clearx {} {
foreach i {1 2 3 4 5 6 7 8 } {
.frame.entry$i delete 0 end } }
proc reportx {} {
global side1 side2 side3 side4 side5
global side6 side7 side8
global testcase_number
console show;
puts "%|table $testcase_number|printed in| tcl wiki format|% "
puts "&| quantity| value| comment, if any|& "
puts "&| testcase number:|$testcase_number | |&"
puts "&| $side1 :|center frequency megahertz | |&"
puts "&| $side2 :|optional| |& "
puts "&| $side3 :|optional| |& "
puts "&| $side4 :|wavelength meters| |&"
puts "&| $side5 :|half wavelength meters | |&"
puts "&| $side6 :|corrected .5L antenna length meters or [expr $side5*39.37008] inches | |&"
puts "&| $side7 :|antenna lead meters | |&"
puts "&| $side8 :|height above ground meters| |&"
}
frame .buttons -bg aquamarine4
::ttk::button .calculator -text "Solve" -command { calculate }
::ttk::button .test2 -text "Testcase1" -command {clearx;fillup 98.1 1. 1.0 2.908 1.45 1.46 .5 5.8}
::ttk::button .test3 -text "Testcase2" -command {clearx;fillup 100.10 1. 1.0 2.85 1.425 1.439 0.5 5.7 }
::ttk::button .test4 -text "Testcase3" -command {clearx;fillup 57.10 1. 1.0 5.0 2.5 2.525 0.50 10.10 }
::ttk::button .clearallx -text clear -command {clearx }
::ttk::button .about -text about -command about
::ttk::button .cons -text report -command { reportx }
::ttk::button .exit -text exit -command {exit}
pack .calculator -in .buttons -side top -padx 10 -pady 5
pack .clearallx .cons .about .exit .test4 .test3 .test2 -side bottom -in .buttons
grid .frame .buttons -sticky ns -pady {0 10}
. configure -background aquamarine4 -highlightcolor brown -relief raised -border 30
wm title . "Twin Lead Folded Dipole Antenna Calculator" Pushbutton Operation
For the push buttons, the recommended procedure is push testcase and fill frame, change first three entries etc, push solve, and then push report. Report allows copy and paste from console.
For testcases in a computer session, the eTCL calculator increments a new testcase number internally, eg. TC(1), TC(2) , TC(3) , TC(N). The testcase number is internal to the calculator and will not be printed until the report button is pushed for the current result numbers. The current result numbers will be cleared on the next solve button. The command { calculate; reportx } or { calculate ; reportx; clearx } can be added or changed to report automatically. Another wrinkle would be to print out the current text, delimiters, and numbers in a TCL wiki style table as
puts " %| testcase $testcase_number | value| units |comment |%" puts " &| volume| $volume| cubic meters |based on length $side1 and width $side2 |&"
Draft Figures
1. TWIN LEAD FOLDED DIPOLE ANTENNA – PHYSICAL LAYOUT
+====================================================================================+
| TWIN LEAD FOLDED DIPOLE ANTENNA (300 Ohm Classic Design) |
+====================================================================================+
| |
| Feedpoint (300 Ohm balanced) |
| │ |
| +-----------+-----------+ |
| | | |
| | Top Conductor | ← Twin Lead (300 Ω) or Ladder Line |
| | | |
| +-----------+-----------+ |
| │ |
| Bottom Conductor (folded back) |
| |
| <---------------- Total Length L ----------------> |
| |
| L ≈ 468 / Frequency_MHz (feet) or 142.5 / f_MHz (meters) |
| Typical: Use 300 Ω TV Twin Lead or 450 Ω Ladder Line |
| |
| Advantages: |
| • ~300 Ohm feed impedance (good match to twin lead) |
| • Wider bandwidth than simple dipole |
| • Easy & cheap to build |
+====================================================================================+
2. eTCL CALCULATOR – BLACK BOX STYLE (TCL/Tk )
+====================================================================================+
| eTCL TWIN LEAD FOLDED DIPOLE CALCULATOR (TCL/Tk ) |
+====================================================================================+
| [ USER / HAM RADIO OPERATOR ] |
| ↓ |
| TCL/Tk 9 GUI (Entry fields + Canvas Diagram + Results) |
| ↓ |
| proc folded_dipole_calc {freq_mhz velocity_factor} { |
| set wavelength [expr {299.792458 / $freq_mhz}] ;# meters |
| set length [expr {0.475 * $wavelength / $velocity_factor}] |
| set impedance 300 |
| return [list $length $impedance] |
| } |
| ↓ |
| Results → Length (meters/feet) | Impedance | Bandwidth Estimate |
| ↓ |
| Canvas Drawing of Antenna + Twin Lead Feed |
+====================================================================================+
| Common Inputs: Frequency (MHz), Velocity Factor (0.8–0.95) |
| Output: Half-wave folded length, SWR estimate, recommended twin-lead length |
+====================================================================================+
3. CONSTRUCTION & DIMENSIONS DIAGRAM
+----------------------------------------------------------------------------------+
| TWIN LEAD FOLDED DIPOLE – CONSTRUCTION DETAILS |
+----------------------------------------------------------------------------------+
| |
| Feed Gap (small) |
| │ |
| ───┬─────────────────────── Twin Lead Top ───────────────────────┬─── |
| │ │ |
| │ Total Length L (≈ 468/f MHz feet) │ |
| │ │ |
| ───┴─────────────────────── Twin Lead Bottom ──────────────────┴─── |
| |
| • Made from 300 Ω Twin Lead or 450 Ω Ladder Line |
| • Ends shorted (folded) |
| • Feed at center gap |
| • Height above ground: ideally ½ wavelength or more |
| |
| Typical Velocity Factor: 0.82 – 0.95 (depends on insulation) |
+----------------------------------------------------------------------------------+4. TCL WIKI STYLE CALCULATOR SUMMARY TABLE
| # | Parameter | Typical Value | Formula / Note | Quibble Notes |
|---|---|---|---|---|
| 1 | Frequency | 98 MHz (FM) | User input | Common FM broadcast band |
| 2 | Total Length | ~4.8 feet | 468 / f_MHz * VF | Half-wave folded |
| 3 | Feed Impedance | ~300 Ω | Characteristic of 2-wire folded | Matches twin lead well |
| 4 | Velocity Factor | 0.82 – 0.95 | Depends on twin lead type | Test and trim in field |
| AUDIT | CHECK | Based on wiki.tcl-lang.org page + standard formulas | Good starter for beginners | Trim antenna 5-10% and measure SWR |
Draft Figures
figure. TWIN LEAD FOLDED DIPOLE ANTENNA: KEY DIMENSIONS
+----------------------------------------------------------------------------------+ | TWIN LEAD FOLDED DIPOLE ANTENNA | | | | overall length ≈ 1/2 wavelength | | feedpoint at center of one conductor pair | | twin-lead spacing remains roughly constant along the fold | | | | |<----------- half-wave conductor path ----------->| | | o==================== feed ====================o | | | | | | | | | | | | | o==============================================o | | | | | feed impedance: ~300 ohms for a standard folded dipole with twin-lead [web:1] | | application: balanced antenna matching to 300-ohm line [web:7] | +----------------------------------------------------------------------------------+
Twin lead diagram
figure. TWIN LEAD FOLDED DIPOLE ANTENNA: GEOMETRY AND FEED
+----------------------------------------------------------------------------------+ | TWIN LEAD FOLDED DIPOLE ANTENNA | | | | end shorted end shorted | | o--------------------------------------------------------------o | | | | | | | | | | | | | | o-------------------- feedpoint split -------------------------o | | | | | | | feed | | | | gap | | | | | conductor path length ≈ 1/2 wavelength | | feedpoint located at center, one conductor pair split for coax or balun feed | | folded structure raises input impedance, commonly near 300 ohms [web:1][web:7] | | twin-lead line is the classic matching line for this antenna [web:1] | +----------------------------------------------------------------------------------+
figure. eTCL TWIN LEAD FOLDED DIPOLE CALCULATOR DEMO
+----------------------------------------------------------------------------------+ | eTCL FOLDED DIPOLE CALCULATOR DEMO | | | | inputs: | | freq MHz | | wavelength factor | | wire spacing | | total wire length | | | | computed values: | | wavelength = 299.792458 / freq | | half-wave length = wavelength / 2 | | folded length ≈ half-wave length | | feed impedance ≈ 300 ohms (rule-of-thumb) [web:1][web:7] | | | | buttons: | | Solve | | Testcase 1 | | Testcase 2 | | clear | | report | | about | +----------------------------------------------------------------------------------+
figure. TWIN LEAD FOLDED DIPOLE ANTENNA: KEY DIMENSIONS
+----------------------------------------------------------------------------------+ | TWIN LEAD FOLDED DIPOLE ANTENNA: KEY DIMENSIONS | | (Half-wave folded dipole using 300Ω twin-lead) | | | | Wavelength λ = (0.95 * 300) / f_MHz (velocity factor ≈ 0.95) | | Total length L ≈ 0.475 * λ (with ~1% end-effect correction) | | | | +-------------------+--------------------------+---------------------------+ | | | parameter | formula | example (100 MHz) | | | +-------------------+--------------------------+---------------------------+ | | | wavelength λ | 0.95*300 / f | 2.85 m | | | | half-wave | λ/2 | 1.425 m | | | | corrected length | 1.01 * (λ/2) | 1.44 m (≈56.7 inches) | | | | height above gnd | ≥ 2 * λ | ≥ 5.7 m | | | | feed impedance | ≈ 300 Ω | matches twin-lead | | | +-------------------+--------------------------+---------------------------+ | | | | Use 4:1 balun when feeding with 75Ω coax. | +----------------------------------------------------------------------------------+
figure. TWIN LEAD FOLDED DIPOLE: GEOMETRY AND CONSTRUCTION
+----------------------------------------------------------------------------------+ | TWIN LEAD FOLDED DIPOLE: GEOMETRY AND CONSTRUCTION | | | | L/2 L/2 | | <-------------------|-------------------> | | | | Feed Gap | | │ | | ─────────[ ]───────────────┐ | | │ (300Ω twin-lead) | | ───────────────────────────┘ | | │ | | Ends shorted | | | | Total length L ≈ corrected half-wave | | Feed at exact center gap. Ends fully shorted. | | Wider conductor (twin-lead) gives better bandwidth. | +----------------------------------------------------------------------------------+
figure. eTCL TWIN LEAD FOLDED DIPOLE CALCULATOR DEMO
+----------------------------------------------------------------------------------+ | eTCL TWIN LEAD FOLDED DIPOLE CALCULATOR DEMO | | (Tcl wiki example calculator) | | | | Inputs → Center frequency (MHz) | | Outputs → Wavelength, corrected length, height | | | | Example at 100.1 MHz: | | λ ≈ 2.847 m | | Corrected L≈ 1.438 m (56.6 inches) | | Height ≈ 5.69 m | | | | Testcase format: | | +---------------+---------------+ | | | freq MHz | corrected L m | | | +---------------+---------------+ | | | 100.1 | 1.438 | | | | 98.1 | 1.467 | | | +---------------+---------------+ | +----------------------------------------------------------------------------------+
figure. WAVELENGTH CALCULATION TABLE
+----------------------------------------------------------------------------------+ | WAVELENGTH CALCULATION TABLE | | (Twin-lead folded dipole, VF=0.95) | | | | +---------------+----------+---------------+---------------+ | | | freq (MHz) | λ (m) | L corr (m) | L (inches) | | | +---------------+----------+---------------+---------------+ | | | 88.1 | 3.239 | 1.636 | 64.4 | | | | 98.1 | 2.905 | 1.467 | 57.8 | | | | 100.1 | 2.847 | 1.438 | 56.6 | | | | 108.1 | 2.638 | 1.332 | 52.4 | | | +---------------+----------+---------------+---------------+ | | | | Formula: L_corr = 1.01 * (0.475 * λ) | +----------------------------------------------------------------------------------+
figure. TWIN LEAD FOLDED DIPOLE vs SIMPLE DIPOLE
+----------------------------------------------------------------------------------+ | TWIN LEAD FOLDED DIPOLE vs SIMPLE DIPOLE | | | | +-------------------+------------------+------------------+ | | | characteristic | simple dipole | folded twin-lead | | | +-------------------+------------------+------------------+ | | | feed impedance | ≈73 Ω | ≈300 Ω | | | | bandwidth | narrower | wider | | | | construction | single wire | twin-lead loop | | | | matching | needs balun | direct twin-lead | | | | gain | ~2.1 dBi | ~2.1 dBi | | | +-------------------+------------------+------------------+ | | | | Folded version preferred when using 300Ω twin-lead. | +----------------------------------------------------------------------------------+
figure. PRACTICAL CONSTRUCTION STEPS
+----------------------------------------------------------------------------------+ | PRACTICAL CONSTRUCTION STEPS | | (Salvage twin-lead or appliance cord) | | | | 1. Calculate corrected length for target frequency | | 2. Cut twin-lead to length + few inches fudge | | 3. Short both ends completely | | 4. Cut small gap at exact center for feed | | 5. Tack or mount horizontally on rafters / wall | | 6. Optional: add 4:1 balun + coax to receiver | | | | Height goal: as high as possible, ideally ≥ 2λ. | +----------------------------------------------------------------------------------+
figure. RADIATION PATTERN AND MOUNTING
+----------------------------------------------------------------------------------+ | RADIATION PATTERN AND MOUNTING | | | | Broadside max (figure-8 pattern) | | ↑ | | <── Antenna ──> (horizontal polarization) | | ↓ | | Nulls off ends | | | | Recommended mounting: | | • Horizontal, as high as possible | | • "V" or corner reflector for extra gain | | • Metal foil or wire reflector behind antenna | | | | Typical gain: 2 dBi (basic), up to 4–5 dBi with reflector. | +----------------------------------------------------------------------------------+ ----
figure. DESIGN RULES OF THUMB
+----------------------------------------------------------------------------------+ | DESIGN RULES OF THUMB | | | | • Velocity factor for twin-lead ≈ 0.95 | | • End effect correction ≈ 1% (multiply half-wave by 1.01) | | • Total length L ≈ 468 / f_MHz (feet) or 142.5 / f_MHz (meters) | | • Minimum height: 2 × wavelength | | • Feed: center gap on folded twin-lead | | • Wider spacing → slightly lower impedance | | | | Always trim slightly longer and prune for best SWR. | +----------------------------------------------------------------------------------+
figure. EXAMPLE CALCULATOR TESTCASES
+----------------------------------------------------------------------------------+ | EXAMPLE CALCULATOR TESTCASES | | (eTCL wiki style) | | | | +----------------+----------+---------------+---------------+ | | | freq MHz | λ (m) | L corr (m) | height (m) | | | +----------------+----------+---------------+---------------+ | | | 98.1 | 2.905 | 1.467 | 5.81 | | | | 100.1 | 2.847 | 1.438 | 5.69 | | | | 57.1 | 4.991 | 2.521 | 9.98 | | | +----------------+----------+---------------+---------------+ | | | | Height = 2 × λ. All dimensions use VF=0.95. | +----------------------------------------------------------------------------------+
figure. FOLDED DIPOLE VARIANTS
+----------------------------------------------------------------------------------+ | FOLDED DIPOLE VARIANTS | | | | • 2-wire folded (standard twin-lead) → 300 Ω | | • 3-wire folded → ~450–600 Ω | | • Terminated folded dipole (T2FD) → broadband | | • Simple dipole (non-folded) → 73 Ω | | | | Twin-lead version is easiest for attic / dorm / scrap material builds. | +----------------------------------------------------------------------------------+
figure. SALVAGE AND MOUNTING OPTIONS
+----------------------------------------------------------------------------------+ | SALVAGE AND MOUNTING OPTIONS | | | | Materials: | | • Old 300Ω TV twin-lead | | • Appliance cord (heavy duty) | | • Speaker wire (as temporary) | | | | Mounting ideas: | | • Tack to rafters or attic beams | | • Varnished wooden board for indoor cosmetic | | • "V" shape for improved gain | | • Add foil reflector behind antenna | +----------------------------------------------------------------------------------+
figure. COMPARISON TABLE: ANTENNA TYPES
+----------------------------------------------------------------------------------+ | COMPARISON TABLE: ANTENNA TYPES | | | | +----------------+----------+----------+----------+ | | | type | Z (Ω) | bandwidth| difficulty| | | +----------------+----------+----------+----------+ | | | simple dipole | 73 | medium | easy | | | | folded twin | 300 | wide | easy | | | | yagi | 50 | narrow | medium | | | | loop | varies | wide | medium | | | +----------------+----------+----------+----------+ | | | | Folded twin-lead dipole offers good balance for FM reception. | +----------------------------------------------------------------------------------+
Comments Section
Please place any comments here, Thanks.
| Category Numerical Analysis | Category Toys | Category Calculator | Category Mathematics | Category Example | Toys and Games | Category Games | Category Application | Category GUI |