21.4MHz Filter a wɔde di dwuma wɔ Walkie-Talkie Field no mu

21.4MHz Filter a wɔde di dwuma wɔ Walkie-Talkie Field no mu

Wɔtaa de 21.4MHz filter no di dwuma sɛ intermediate frequency (IF) filter wɔ walkie-talkie receivers mu, na ne dwumadie no na ɛkyerɛ walkie-talkies ho nsɛnkyerɛnneɛ titire mmienu no tẽẽ: selectivity ne sensitivity.

Yɛbɛkyerɛkyerɛ mu akɔ akyiri afi afã horow a edidi so yi mu:

1. Dɛn ne "Mfinimfini Frequency" a ɛwɔ Walkie-Talkie mu?

Sɛnea ɛbɛyɛ a wobenya adwumayɛ pa no, walkie-talkies (ne superheterodyne agyefo afoforo nso) nhyɛ radio frequency (RF) nsɛnkyerɛnne a wɔagye no mu den tẽẽ na ɛnnyɛ demodulate (sɛ nhwɛso no, 400-470MHz). Mmom no, wɔfa anammɔn a edidi so yi:1 Mixing: Wɔde RF sɛnkyerɛnne a ɛwɔ frequency a ɛkorɔn a wɔanya no frafra signal a local oscillator no de ba no mu.2 Generation of Intermediate Frequency: Sɛ wɔde afra wie a, wɔyɛ signal foforo a ɛwɔ fixed frequency, a ɛyɛ mfinimfini frequency.3 IF Amplification and Filtering: Wɔma fixed IF signal no yɛ kɛse kɛse na wɔyiyi mu katee.

Mfaso a ɛwɔ "superheterodyne" nhyehyɛe no so ne sɛ mfaso ne selectivity dodow no ara (tumi a wɔde yiyi channel interference a ɛbɛn hɔ) no nam saa fixed IF fã yi so nya, na ɛma circuit no nhyehyɛe no gyina pintinn na ɛyɛ adwuma yiye.

2. Dɛn nti na 21.4MHz?

21.4MHz yɛ standard IF frequency a agye din paa wɔ VHF/UHF bands mu (a bands a walkie-talkies de di dwuma ka ho). Ntease ahorow a ɛwɔ abakɔsɛm ne mfiridwuma mu no bi ne:

Mfiridwuma nkɔnsɔnkɔnsɔn a ɛho akokwaw: Wɔ 21.4MHz frequency no ho no, filters, amplifiers, ne nneɛma a ɛfa ho a ɛho akokwaw, ɛyɛ den, na ɛho ka sua-ɛdɔɔso.

Kari a ɛkari pɛ wɔ adwumayɛ ne ɛka ntam: Saa mpɛn dodow yi korɔn araa ma ebetumi asiw mfonini a ɛtwetwe adwene no ano yiye (asɛm a ɛtaa ba wɔ agyede mu); bere koro no ara mu no, ɛba fam araa ma ɛbɛyɛ mmerɛw sɛ wɔbɛyɛ nhyehyɛe ne ne yɛ a ɛkorɔn-Q (quality factor) filters (te sɛ crystal filters ne ceramic filters).

Abakɔsɛm mu agyapadeɛ: Wɔde saa frequency yi adi dwuma wɔ nkitahodiɛ adwumayɛ mu mfeɛ du du pii, na wɔayɛ walkie-talkie chips ne ano aduru a wɔagye din pii atwa saa frequency a ɛwɔ ntam yi ho ahyia.

3. Dwuma titiriw a 21.4MHz Filter di wɔ Walkie-Talkies mu

Wɔ 21.4MHz IF ɔfa no mu no, filter no ne "apon ano hwɛfo" ankasa. Ne dwumadie ho hia paa:1 Ma Selectivity atu mpɔn

Dwumadi: Selectivity kyerɛ tumi a nea ogye no tumi hu nsonsonoe a ɛda sɛnkyerɛnne a ɔpɛ no ntam wɔ nsɛnkyerɛnne pii mu na esiw nsɛnkyerɛnne a ɛbɛn no a ɛtwetwe akwan no ano.

Sɛnea ɛyɛ adwuma: 21.4MHz filter no wɔ frequency response curve a ɛyɛ den yiye (mpɛn pii no te sɛ "brick wall"). Ɛma kwan ma sɛnkyerɛnne fã bi a 21.4MHz yɛ mfinimfini ne bandwidth a ɛyɛ pɛpɛɛpɛ yiye nkutoo fa mu (sɛ nhwɛso no, ±6.25kHz, ±7.5kHz, ±12.5kHz a wɔtaa de di dwuma wɔ walkie-talkies mu, a ɛne akwan horow ntam kwan hyia).

Nsunsuansoɔ a mfasoɔ wɔ so: Sɛ radio dwumadibea mmienu a ɛwɔ frequency a ɛbɛn paa no de nsɛm kɔ bere koro mu a, walkie-talkie a wɔde 21.4MHz filter a ɛyɛ adwuma kɛse-ahyɛ mu no betumi ate radio dwumadibea a wɔde wɔn ani asi so no nnyigyei pefee, bere a esiw kwan foforo a ɛbɛn no no sɛnkyerɛnne ano yiye na wɔakwati crosstalk. Sɛ saa filter yi nni hɔ anaasɛ filter a ɛnyɛ adwuma yie a, wobɛte "channel crosstalk" dede.

2 Ma Nkate mu Ntu mpɔn

Dwumadi: Nkate kyerɛ tumi a nea ogye no tumi gye nsɛnkyerɛnne a ɛyɛ mmerɛw.

Sɛnea ɛyɛ adwuma: Ansa na wɔbɛma IF sɛnkyerɛnne no ayɛ kɛse no, wɔde filter no di kan yi-of-band dede ne ntwitwiridii no fi hɔ. Saa kwan yi so no, amplification titiriw ne "hotew" mfaso sɛnkyerɛnne no ankasa. Sɛ wɔyɛ amplification a wɔmfa filtering nhyɛ mu a, out-of-band noise nso bɛhyɛ amplified, na ɛnam so ama signal a etu mpɔn a ɛyɛ mmerɛw no amene.

Nsunsuansoɔ a mfasoɔ wɔ so: Ɛma wo walkie-talkie no kwan ma ɛkura nkitahodiɛ a nteaseɛ mu wɔ akyirikyiri mpo anaasɛ ɛwɔ nsɛnkyerɛnneɛ a ɛyɛ mmerɛ.

4. Nneɛma ahorow a ɛwɔ 21.4MHz Filters

Wɔ walkie-talkies mu no, 21.4MHz filters a wɔtaa de di dwuma no titiriw de ahorow a edidi so yi ka ho:

Ceramic Filter a Wɔde Yɛ Nneɛma:

Nneɛma a ɛwom: Ɛho ka sua, ne kɛse sua, wotumi de ho to so kɛse, na ɛho nhia sɛ wɔyɛ nsakrae biara.

Dwumadie: Wɔde di dwuma kɛseɛ wɔ mid-to{1}}low-end walkie-talkies mu, na ne dwumadie dɔɔso sɛ ɛbɛdi ahiadeɛ dodoɔ no ara a wɔtaa de di dwuma no ho dwuma. Ne bandwidth ne shape factor (a ɛkyerɛ sɛnea filter no ano yɛ toro) taa yɛ bɔne kakra sen crystal filters nanso eye sen LC filters kɛse.

Crystal Filter a Wɔde Yɛ Nneɛma:

Features: Ɛwɔ Q bo a ɛkorɔn yiye, enti selectivity no ye yiye, na shape factor no bɛn tebea a eye sen biara no yiye.

Dwumadie: Wɔtaa de di dwuma wɔ high-end professional walkie-talkies anaa mmere a ɛhwehwɛ sɛ wɔde anti-interference tumi a ɛkorɔn yiye. Ɛka a wɔbɔ no dɔɔso sen nea wɔde yɛ dɔte a wɔde yiyi nneɛma mu.