Partially Collapse Telescoping Antenna to Change Effective Length
I recently purchased a cheap RTL-SDR kit to experiment with SDRs and different frequency bands. This kit came with 23cm and 100cm telescoping antennas. I now wish to use the 100cm antenna to pick up NOAA APT signals at 137 MHz. Many sites with instructions for a V-Dipole antenna for this purpose indicate that a 53cm half-wave antenna works well.
Is there something special about telescoping antennas such that they only work when fully extended, or can I partially retract the 100cm antennas to 53cm to get the proper length?
antenna dipole
asked 3 hours ago
Alex Wulff
1112
New contributor
Alex Wulff is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
I recently purchased a cheap RTL-SDR kit to experiment with SDRs and different frequency bands. This kit came with 23cm and 100cm telescoping antennas. I now wish to use the 100cm antenna to pick up NOAA APT signals at 137 MHz. Many sites with instructions for a V-Dipole antenna for this purpose indicate that a 53cm half-wave antenna works well.
Is there something special about telescoping antennas such that they only work when fully extended, or can I partially retract the 100cm antennas to 53cm to get the proper length?
antenna dipole
asked 3 hours ago
Alex Wulff
1112
New contributor
Alex Wulff is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Take note that for a dipole, the length would be ~54 cm per side.(per leg).
– Glenn W9IQ
1 hour ago
add a comment |
I recently purchased a cheap RTL-SDR kit to experiment with SDRs and different frequency bands. This kit came with 23cm and 100cm telescoping antennas. I now wish to use the 100cm antenna to pick up NOAA APT signals at 137 MHz. Many sites with instructions for a V-Dipole antenna for this purpose indicate that a 53cm half-wave antenna works well.
Is there something special about telescoping antennas such that they only work when fully extended, or can I partially retract the 100cm antennas to 53cm to get the proper length?
antenna dipole
asked 3 hours ago
Alex Wulff
1112
New contributor
Alex Wulff is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
I recently purchased a cheap RTL-SDR kit to experiment with SDRs and different frequency bands. This kit came with 23cm and 100cm telescoping antennas. I now wish to use the 100cm antenna to pick up NOAA APT signals at 137 MHz. Many sites with instructions for a V-Dipole antenna for this purpose indicate that a 53cm half-wave antenna works well.
Is there something special about telescoping antennas such that they only work when fully extended, or can I partially retract the 100cm antennas to 53cm to get the proper length?
antenna dipole
antenna dipole
asked 3 hours ago
Alex Wulff
1112
New contributor
Alex Wulff is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 3 hours ago
Alex Wulff
1112
New contributor
Alex Wulff is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 3 hours ago
Alex Wulff
1112
New contributor
Alex Wulff is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 3 hours ago
Alex Wulff
1112
asked 3 hours ago
Alex Wulff
1112
1112
New contributor
Alex Wulff is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
Alex Wulff is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Alex Wulff is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Take note that for a dipole, the length would be ~54 cm per side.(per leg).
– Glenn W9IQ
1 hour ago
add a comment |
Take note that for a dipole, the length would be ~54 cm per side.(per leg).
– Glenn W9IQ
1 hour ago
Take note that for a dipole, the length would be ~54 cm per side.(per leg).
– Glenn W9IQ
1 hour ago
Take note that for a dipole, the length would be ~54 cm per side.(per leg).
– Glenn W9IQ
1 hour ago
add a comment |
3 Answers
3
active
oldest
votes
Yes, you can partially collapse a telescoping antenna. There are no special considerations versus other types of antenna elements / monopoles.
There is a slight effect from the thickness of the antenna — thicker conductors, such as the telescoping elements closer to the base, exhibit more bandwidth (less selectivity). This is usually not very significant at all for receiving purposes, but if you're trying to pick out a single signal then you can theoretically get a small reduction of out-of-band interference by extending the thinner sections of the antenna rather than the thicker ones, provided that you also get the length exactly right (adjusting to maximize the power of the received signal).
answered 2 hours ago
Kevin Reid AG6YO♦
15.4k32965
add a comment |
53cm is ~1/4 wavelength on 137 MHz. I can't tell if your antenna is a single vertical monopole element or a rabbit ears type dipole. Assuming it is a single vertical element, if you provide a ground plane and set the length to 53 cm, you will have a resonant ground plane vertical on ~137 MHz. The ground plane could be a pizza pan or metal filing cabinet, etc. and coupling to it can be either coax braid direct wiring or capacitive coupling through magnets (if any).
If it is a rabbit ears type dipole, each element needs to be set to 53 cm and you can skip the ground plane.
answered 2 hours ago
w5dxp
3365
add a comment |
Telescoping antennas work at any length you set them. They are always connected internally.
Speaking from experience, being able to move the antenna around to find the best signal makes a much bigger difference than fine tuning its length.
answered 13 mins ago
gbarry
1012
add a comment |
Your Answer
StackExchange.ifUsing("editor", function () {
return StackExchange.using("mathjaxEditing", function () {
StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
});
});
}, "mathjax-editing");
StackExchange.ifUsing("editor", function () {
return StackExchange.using("schematics", function () {
StackExchange.schematics.init();
});
}, "cicuitlab");
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "520"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});
function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});
}
});
Alex Wulff is a new contributor. Be nice, and check out our Code of Conduct.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fham.stackexchange.com%2fquestions%2f12470%2fpartially-collapse-telescoping-antenna-to-change-effective-length%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
Yes, you can partially collapse a telescoping antenna. There are no special considerations versus other types of antenna elements / monopoles.
There is a slight effect from the thickness of the antenna — thicker conductors, such as the telescoping elements closer to the base, exhibit more bandwidth (less selectivity). This is usually not very significant at all for receiving purposes, but if you're trying to pick out a single signal then you can theoretically get a small reduction of out-of-band interference by extending the thinner sections of the antenna rather than the thicker ones, provided that you also get the length exactly right (adjusting to maximize the power of the received signal).
answered 2 hours ago
Kevin Reid AG6YO♦
15.4k32965
add a comment |
Yes, you can partially collapse a telescoping antenna. There are no special considerations versus other types of antenna elements / monopoles.
There is a slight effect from the thickness of the antenna — thicker conductors, such as the telescoping elements closer to the base, exhibit more bandwidth (less selectivity). This is usually not very significant at all for receiving purposes, but if you're trying to pick out a single signal then you can theoretically get a small reduction of out-of-band interference by extending the thinner sections of the antenna rather than the thicker ones, provided that you also get the length exactly right (adjusting to maximize the power of the received signal).
answered 2 hours ago
Kevin Reid AG6YO♦
15.4k32965
add a comment |
Yes, you can partially collapse a telescoping antenna. There are no special considerations versus other types of antenna elements / monopoles.
There is a slight effect from the thickness of the antenna — thicker conductors, such as the telescoping elements closer to the base, exhibit more bandwidth (less selectivity). This is usually not very significant at all for receiving purposes, but if you're trying to pick out a single signal then you can theoretically get a small reduction of out-of-band interference by extending the thinner sections of the antenna rather than the thicker ones, provided that you also get the length exactly right (adjusting to maximize the power of the received signal).
answered 2 hours ago
Kevin Reid AG6YO♦
15.4k32965
Yes, you can partially collapse a telescoping antenna. There are no special considerations versus other types of antenna elements / monopoles.
There is a slight effect from the thickness of the antenna — thicker conductors, such as the telescoping elements closer to the base, exhibit more bandwidth (less selectivity). This is usually not very significant at all for receiving purposes, but if you're trying to pick out a single signal then you can theoretically get a small reduction of out-of-band interference by extending the thinner sections of the antenna rather than the thicker ones, provided that you also get the length exactly right (adjusting to maximize the power of the received signal).
answered 2 hours ago
Kevin Reid AG6YO♦
15.4k32965
answered 2 hours ago
Kevin Reid AG6YO♦
15.4k32965
answered 2 hours ago
Kevin Reid AG6YO♦
15.4k32965
answered 2 hours ago
Kevin Reid AG6YO♦
15.4k32965
15.4k32965
add a comment |
add a comment |
53cm is ~1/4 wavelength on 137 MHz. I can't tell if your antenna is a single vertical monopole element or a rabbit ears type dipole. Assuming it is a single vertical element, if you provide a ground plane and set the length to 53 cm, you will have a resonant ground plane vertical on ~137 MHz. The ground plane could be a pizza pan or metal filing cabinet, etc. and coupling to it can be either coax braid direct wiring or capacitive coupling through magnets (if any).
If it is a rabbit ears type dipole, each element needs to be set to 53 cm and you can skip the ground plane.
answered 2 hours ago
w5dxp
3365
add a comment |
53cm is ~1/4 wavelength on 137 MHz. I can't tell if your antenna is a single vertical monopole element or a rabbit ears type dipole. Assuming it is a single vertical element, if you provide a ground plane and set the length to 53 cm, you will have a resonant ground plane vertical on ~137 MHz. The ground plane could be a pizza pan or metal filing cabinet, etc. and coupling to it can be either coax braid direct wiring or capacitive coupling through magnets (if any).
If it is a rabbit ears type dipole, each element needs to be set to 53 cm and you can skip the ground plane.
answered 2 hours ago
w5dxp
3365
add a comment |
53cm is ~1/4 wavelength on 137 MHz. I can't tell if your antenna is a single vertical monopole element or a rabbit ears type dipole. Assuming it is a single vertical element, if you provide a ground plane and set the length to 53 cm, you will have a resonant ground plane vertical on ~137 MHz. The ground plane could be a pizza pan or metal filing cabinet, etc. and coupling to it can be either coax braid direct wiring or capacitive coupling through magnets (if any).
If it is a rabbit ears type dipole, each element needs to be set to 53 cm and you can skip the ground plane.
answered 2 hours ago
w5dxp
3365
53cm is ~1/4 wavelength on 137 MHz. I can't tell if your antenna is a single vertical monopole element or a rabbit ears type dipole. Assuming it is a single vertical element, if you provide a ground plane and set the length to 53 cm, you will have a resonant ground plane vertical on ~137 MHz. The ground plane could be a pizza pan or metal filing cabinet, etc. and coupling to it can be either coax braid direct wiring or capacitive coupling through magnets (if any).
If it is a rabbit ears type dipole, each element needs to be set to 53 cm and you can skip the ground plane.
answered 2 hours ago
w5dxp
3365
answered 2 hours ago
w5dxp
3365
answered 2 hours ago
w5dxp
3365
answered 2 hours ago
w5dxp
3365
3365
add a comment |
add a comment |
Telescoping antennas work at any length you set them. They are always connected internally.
Speaking from experience, being able to move the antenna around to find the best signal makes a much bigger difference than fine tuning its length.
answered 13 mins ago
gbarry
1012
add a comment |
Telescoping antennas work at any length you set them. They are always connected internally.
Speaking from experience, being able to move the antenna around to find the best signal makes a much bigger difference than fine tuning its length.
answered 13 mins ago
gbarry
1012
add a comment |
Telescoping antennas work at any length you set them. They are always connected internally.
Speaking from experience, being able to move the antenna around to find the best signal makes a much bigger difference than fine tuning its length.
answered 13 mins ago
gbarry
1012
Telescoping antennas work at any length you set them. They are always connected internally.
Speaking from experience, being able to move the antenna around to find the best signal makes a much bigger difference than fine tuning its length.
answered 13 mins ago
gbarry
1012
answered 13 mins ago
gbarry
1012
answered 13 mins ago
gbarry
1012
answered 13 mins ago
gbarry
1012
1012
add a comment |
add a comment |
Alex Wulff is a new contributor. Be nice, and check out our Code of Conduct.
Alex Wulff is a new contributor. Be nice, and check out our Code of Conduct.
Alex Wulff is a new contributor. Be nice, and check out our Code of Conduct.
Alex Wulff is a new contributor. Be nice, and check out our Code of Conduct.
Thanks for contributing an answer to Amateur Radio Stack Exchange!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
Use MathJax to format equations. MathJax reference.
To learn more, see our tips on writing great answers.
Some of your past answers have not been well-received, and you're in danger of being blocked from answering.
Please pay close attention to the following guidance:
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fham.stackexchange.com%2fquestions%2f12470%2fpartially-collapse-telescoping-antenna-to-change-effective-length%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Take note that for a dipole, the length would be ~54 cm per side.(per leg).
– Glenn W9IQ
1 hour ago